Electrical conductivity measurements are reported for solutions in trifluoromethanesulfonic acid of a number of simple and complex bases, including univalent and divalent metal trifluoromethanesulfonates. The univalent metal salts, water, aniline, and acetic acid behave as fully dissociated bases, while the alkaline earth metal salts show considerable ion association. The trifluoromethanesulfonate anion appears to have an abnormally high mobility, as compared to the metal cations, and is believed to conduct by a proton-transfer mechanism. Dissociation constants for some weak organic bases and association constants for strontium and barium trifluoromethanesulfonates are estimated. Sulfuric acid behaves as a weak electrolyte, while sulfur trioxide is effectively a non-electrolyte. The conductivities of potassium nitrate and potassium dihydrogenphosphate are consistent with the formation of the nitryl cation and the phosphate acidium ion, respectively.