Raman spectra of solutions of dmso (dimethyl sulphoxide) are studied in the S=O stretching region by second derivative analysis. Broad bands observed in the normal Raman spectra show well resolved components in the derivative plots. On the basis of the various components obtained in these plots for solutions of dmso in carbon tetrachloride and water, existence of equilibria between various associated species, involving dipolar and hydrogen bonding interactions, is suggested. It is concluded that solutions of dmso in CCl4 may have monomers, cyclic and linear dimers and polymers, whereas its aqueous solutions show the existence of 1:1 and 1:2 hydrogen bonded complexes of water with dmso in addition to smaller concentrations of monomers, dimers and polymers. © 1985 Indian Academy of Sciences.