An efficient soft docking algorithm is described to predict the mode of binding between two proteins based on the three-dimensional structures of molecules. The molecular model used in this work was grounded on the "simplified protein" model used in Janin's docking algorithm. The side chain flexibility of the amino acid residues Arg, Lys, Asp, Glu and Met at the protein surface was considered through softening the molecular surface. A double filtering technique was used to eliminate most of the unlike binding modes. The energy minimization was performed on the retained structures, and then these structures were evaluated with the scoring function which included electrostatic, desolvation and van der Waals energy terms. The 26 complexes were used to test this docking algorithm and good results were obtained. The native-like conformations of all the complexes were all found, of which 20 were ranked in the top 10.