Department of Chemistry, Himachal Pradesh University, Summer Hill, Shimla-171 005 Manuscript received 5 February 1991, revised 27 August 1992, accepted 1 September 1992 Viscosities of some solutes have been measured in dimethylformamide (DMF), ethyl methyl ketone (EMK) and DMF+EMK mixtures at 25°. The viscosity data has been analysed by the Jones-Dole equation for electrolytes to evaluate A and B coefficients of viscosity. A and B coefficients for all the electrolytes are positive and B-coefficients have been split up into the contribution due to individual ions (B ± values). An examination of B± coefficients as a function of solvent composition indicates that B+ and B_ values of tetraalkylammonium cations and anions respectively remain almost constant, whereas B+ values for Na+ and K+ first increase, show a maximum and then decrease with the addition of EMK content in the DMF+EMK solvent mixtures. This shows that there is no preferential solvation for tetraalkylammonium ions but Na+ and K+ ions exhibit preferential solvation in DMF+EMK mixtures.