Systematic determinations of electrical conductivities of sodium penicillin G, potassium penicillin G, and potassium penicillin V in the 278.15-313.15 K temperature range are reported. These conductivities are examined by applying the Quint-Viallard conductivity equations and the Debye-Huckel equations for activity coefficients. Determined dissociation constants and the limiting conductances of penicillin anions are based on the assumption that in dilute aqueous solutions, penicillin salts behave as acidic salts of dibasic acids, which are the final products of degradation reactions in acidic media.