An exploratory voltammetric study of several acids, some representative metal ions, a few quinones, and oxygen has been made in the solvent dimethylsulfoxide (DMSO). Perchloric, sulfuric, and hydrochloric acids were found to be monoprotic strong acids in DMSO. Cobalt (II) and nickel (II) are reduced irreversibly at the dropping mercury electrode with large overpotentials indicating strong solvation. Polarograms of quinones showed two cathodic waves of unequal height in the absence of proton donor. The effect of proton donor on the polarograms of quinones was studied. The mechanism of the reduction of quinones in DMSO is discussed. Rotated platinum and rotated mercury pool electrodes can be used to advantage in DMSO.