diff --git a/Code/GraphMol/Descriptors/Lipinski.cpp b/Code/GraphMol/Descriptors/Lipinski.cpp
index fa8f42522..996b00e43 100644
--- a/Code/GraphMol/Descriptors/Lipinski.cpp
+++ b/Code/GraphMol/Descriptors/Lipinski.cpp
@@ -89,6 +89,7 @@ namespace RDKit{
     }
 
     SMARTSCOUNTFUNC(NumRotatableBonds, "[!$(*#*)&!D1]-&!@[!$(*#*)&!D1]", "1.0.1" ) ;
+    SMARTSCOUNTFUNC(NumStrictRotatableBonds, "[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])&!$([CD3](=[N,O,S])-!@[#7,O,S!D1])&!$([#7,O,S!D1]-!@[CD3]=[N,O,S])&!$([CD3](=[N+])-!@[#7!D1])&!$([#7!D1]-!@[CD3]=[N+])]-!@[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])]", "1.0.0" ) ;
     //SMARTSCOUNTFUNC(NumHBD, "[$([N;!H0;v3]),$([N;!H0;+1;v4]),$([O,S;H1;+0]),$([n;H1;+0])]","2.0.1" ) ;
     SMARTSCOUNTFUNC(NumHBD, "[N&!H0&v3,N&!H0&+1&v4,O&H1&+0,S&H1&+0,n&H1&+0]","2.0.1" ) ;
     SMARTSCOUNTFUNC(NumHBA, "[$([O,S;H1;v2]-[!$(*=[O,N,P,S])]),$([O,S;H0;v2]),$([O,S;-]),$([N;v3;!$(N-*=!@[O,N,P,S])]),$([nH0,o,s;+0])]","2.0.1") ;
diff --git a/Code/GraphMol/Descriptors/Lipinski.h b/Code/GraphMol/Descriptors/Lipinski.h
index 97f1d005c..c52b46605 100644
--- a/Code/GraphMol/Descriptors/Lipinski.h
+++ b/Code/GraphMol/Descriptors/Lipinski.h
@@ -31,6 +31,10 @@ namespace RDKit{
     //! calculates the number of rotatable bonds
     unsigned int calcNumRotatableBonds(const ROMol &mol);
 
+    extern const std::string NumStrictRotatableBondsVersion;
+    //! calculates the number of rotatable bonds more strictly, excluding amides, esters etc
+    unsigned int calcNumStrictRotatableBonds(const ROMol &mol);
+
     extern const std::string NumHBDVersion;
     //! calculates the number of H-bond donors
     unsigned int calcNumHBD(const ROMol &mol);
diff --git a/Code/GraphMol/Descriptors/Wrap/rdMolDescriptors.cpp b/Code/GraphMol/Descriptors/Wrap/rdMolDescriptors.cpp
index 2b12747d5..165a4fe68 100644
--- a/Code/GraphMol/Descriptors/Wrap/rdMolDescriptors.cpp
+++ b/Code/GraphMol/Descriptors/Wrap/rdMolDescriptors.cpp
@@ -770,6 +770,12 @@ BOOST_PYTHON_MODULE(rdMolDescriptors) {
 	      (python::arg("mol")),
               docString.c_str());
   python::scope().attr("_CalcNumRotatableBonds_version")=RDKit::Descriptors::NumRotatableBondsVersion;
+  docString="returns a strict count of the number of rotatable bonds for a molecule";
+  python::def("CalcNumStrictRotatableBonds",
+	      RDKit::Descriptors::calcNumStrictRotatableBonds,
+	      (python::arg("mol")),
+              docString.c_str());
+  python::scope().attr("_CalcNumStrictRotatableBonds_version")=RDKit::Descriptors::NumStrictRotatableBondsVersion;
   docString="returns the number of rings for a molecule";
   python::def("CalcNumRings",
 	      RDKit::Descriptors::calcNumRings,
diff --git a/Code/JavaWrappers/Lipinski.java b/Code/JavaWrappers/Lipinski.java
index 0d40b20b6..2af4ffe94 100644
--- a/Code/JavaWrappers/Lipinski.java
+++ b/Code/JavaWrappers/Lipinski.java
@@ -52,6 +52,7 @@ public class Lipinski {
 	//  from the graph). So the bond in [2H]C([2H])([2H])C([2H])([2H])[2H] *is* considered
 	//  rotatable.
 	static ROMol RotatableBondSmarts = RWMol.MolFromSmarts("[!$(*#*)&!D1]-&!@[!$(*#*)&!D1]");
+	static ROMol StrictRotatableBondSmarts = RWMol.MolFromSmarts("[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])&!$([CD3](=[N,O,S])-!@[#7,O,S!D1])&!$([#7,O,S!D1]-!@[CD3]=[N,O,S])&!$([CD3](=[N+])-!@[#7!D1])&!$([#7!D1]-!@[CD3]=[N+])]-!@[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])]");
 	static ROMol NHOHSmarts = RWMol.MolFromSmarts("[#8H1,#7H1,#7H2,#7H3]");
 	static ROMol NOCountSmarts = RWMol.MolFromSmarts("[#7,#8]");
 
@@ -71,6 +72,9 @@ public class Lipinski {
 	public static int getRotatableBondCount(ROMol mol) {
 		return getMatchCount(mol, RotatableBondSmarts);
 	}
+	public static int getStrictRotatableBondCount(ROMol mol) {
+		return getMatchCount(mol, StrictRotatableBondSmarts);
+	}
 	public static int getNHOHCount(ROMol mol) {
 		return getMatchCount(mol, NHOHSmarts);
 	}
diff --git a/Code/PgSQL/rdkit/adapter.cpp b/Code/PgSQL/rdkit/adapter.cpp
index a75bb394e..c08b62ae6 100644
--- a/Code/PgSQL/rdkit/adapter.cpp
+++ b/Code/PgSQL/rdkit/adapter.cpp
@@ -435,6 +435,7 @@ MOLDESCR(NumAliphaticCarbocycles,RDKit::Descriptors::calcNumAliphaticCarbocycles
 MOLDESCR(NumSaturatedCarbocycles,RDKit::Descriptors::calcNumSaturatedCarbocycles,int)
 
 MOLDESCR(NumRotatableBonds,RDKit::Descriptors::calcNumRotatableBonds,int)
+MOLDESCR(NumStrictRotatableBonds,RDKit::Descriptors::calcNumStrictRotatableBonds,int)
 MOLDESCR(Chi0v,RDKit::Descriptors::calcChi0v,double)
 MOLDESCR(Chi1v,RDKit::Descriptors::calcChi1v,double)
 MOLDESCR(Chi2v,RDKit::Descriptors::calcChi2v,double)
diff --git a/Code/PgSQL/rdkit/mol_op.c b/Code/PgSQL/rdkit/mol_op.c
index f2e02baa0..7e39ec139 100644
--- a/Code/PgSQL/rdkit/mol_op.c
+++ b/Code/PgSQL/rdkit/mol_op.c
@@ -190,6 +190,7 @@ MOLDESCR(hbd,MolHBD,INT32)
 MOLDESCR(numatoms,MolNumAtoms,INT32)
 MOLDESCR(numheavyatoms,MolNumHeavyAtoms,INT32)
 MOLDESCR(numrotatablebonds,MolNumRotatableBonds,INT32)
+MOLDESCR(numstrictrotatablebonds,MolNumStrictRotatableBonds,INT32)
 MOLDESCR(numheteroatoms,MolNumHeteroatoms,INT32)
 MOLDESCR(numrings,MolNumRings,INT32)
 MOLDESCR(numaromaticrings,MolNumAromaticRings,INT32)
diff --git a/Code/PgSQL/rdkit/rdkit.h b/Code/PgSQL/rdkit/rdkit.h
index b783a90f8..794479164 100644
--- a/Code/PgSQL/rdkit/rdkit.h
+++ b/Code/PgSQL/rdkit/rdkit.h
@@ -117,6 +117,7 @@ extern "C" {
   int MolNumAtoms(CROMol i);
   int MolNumHeavyAtoms(CROMol i);
   int MolNumRotatableBonds(CROMol i);
+  int MolNumStrictRotatableBonds(CROMol i);
   int MolNumHeteroatoms(CROMol i);
   int MolNumRings(CROMol i);
   int MolNumAromaticRings(CROMol i);
diff --git a/Code/PgSQL/rdkit/rdkit.sql.in b/Code/PgSQL/rdkit/rdkit.sql.in
index ef9a419b3..c093a2c2f 100644
--- a/Code/PgSQL/rdkit/rdkit.sql.in
+++ b/Code/PgSQL/rdkit/rdkit.sql.in
@@ -300,6 +300,11 @@ RETURNS integer
 AS 'MODULE_PATHNAME'
 LANGUAGE C STRICT IMMUTABLE;
 
+CREATE OR REPLACE FUNCTION mol_numstrictrotatablebonds(mol)
+RETURNS integer
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
 CREATE OR REPLACE FUNCTION mol_numatoms(mol)
 RETURNS integer
 AS 'MODULE_PATHNAME'
diff --git a/Code/PgSQL/rdkit/rdkit.sql91.in b/Code/PgSQL/rdkit/rdkit.sql91.in
index e0ec04d0f..98effd0c3 100644
--- a/Code/PgSQL/rdkit/rdkit.sql91.in
+++ b/Code/PgSQL/rdkit/rdkit.sql91.in
@@ -371,6 +371,11 @@ RETURNS integer
 AS 'MODULE_PATHNAME'
 LANGUAGE C STRICT IMMUTABLE;
 
+CREATE OR REPLACE FUNCTION mol_numstrictrotatablebonds(mol)
+RETURNS integer
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
 CREATE OR REPLACE FUNCTION mol_numatoms(mol)
 RETURNS integer
 AS 'MODULE_PATHNAME'
diff --git a/rdkit/Chem/Lipinski.py b/rdkit/Chem/Lipinski.py
index 0f5b36cd2..474e471ed 100755
--- a/rdkit/Chem/Lipinski.py
+++ b/rdkit/Chem/Lipinski.py
@@ -45,6 +45,11 @@ HeteroatomSmarts = Chem.MolFromSmarts('[!#6;!#1]')
 #  from the graph). So the bond in [2H]C([2H])([2H])C([2H])([2H])[2H] *is* considered
 #  rotatable.
 RotatableBondSmarts = Chem.MolFromSmarts('[!$(*#*)&!D1]-&!@[!$(*#*)&!D1]')
+#  Under Strict rules a bond is rotatable iff it is a single non-ring bond where neither atom
+#  is terminal or in a terminal group or where a conjugated system involving amides, esters, 
+#  sulfonamides etc appear. A terminal group is defined as and of the following: C(F)(F)F,
+#  C(Cl)(Cl)Cl, C(Br)(Br)Br or C([CH3])([CH3])[CH3]
+StrictRotatableBondSmarts = Chem.MolFromSmarts('[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])&!$([CD3](=[N,O,S])-!@[#7,O,S!D1])&!$([#7,O,S!D1]-!@[CD3]=[N,O,S])&!$([CD3](=[N+])-!@[#7!D1])&!$([#7!D1]-!@[CD3]=[N+])]-!@[!$(*#*)&!D1&!$(C(F)(F)F)&!$(C(Cl)(Cl)Cl)&!$(C(Br)(Br)Br)&!$(C([CH3])([CH3])[CH3])]')
 NHOHSmarts = Chem.MolFromSmarts('[#8H1,#7H1,#7H2,#7H3]')
 NOCountSmarts = Chem.MolFromSmarts('[#7,#8]')
 
@@ -68,6 +73,10 @@ NumRotatableBonds = lambda x:rdMolDescriptors.CalcNumRotatableBonds(x)
 NumRotatableBonds.__doc__="Number of Rotatable Bonds"
 NumRotatableBonds.version="1.0.0"
 _RotatableBonds = lambda x,y=RotatableBondSmarts:x.GetSubstructMatches(y,uniquify=1)
+NumStrictRotatableBonds = lambda x:rdMolDescriptors.CalcNumStrictRotatableBonds(x)
+NumStrictRotatableBonds.__doc__="Stricter count of the number of Rotatable Bonds"
+NumStrictRotatableBonds.version="1.0.0"
+_StrictRotatableBonds = lambda x,y=StrictRotatableBondSmarts:x.GetSubstructMatches(y,uniquify=1)
 NOCount = lambda x:rdMolDescriptors.CalcNumLipinskiHBA(x)
 NOCount.__doc__="Number of Nitrogens and Oxygens"
 NOCount.version="1.0.0"