The molecular configuration of hydrogen disulphide has been discused and C2- symmetrical structure model has been proposed The force constants of HgSg have been calculated, by means of a guadratic poten- tial fonctipn assumed for the sarae model. 2509, 882, 509 and 202 cm“' symmetrical, and 2577 and 886 cm"* unsymmetrical fundemantal vibration frequencies which were detected both in the IR and R, have been used for the calculation of the force constants.