Triethylamine (TEA) was evaluated as a competing base for the retention control and peak shape improvement in the reversed-phase high-performance liquid chromatographic (RP-HPLC) analysis of selected acidic, basic, and neutral drugs. The effects of this amine on the capacity factor and theoretical plate number values of ephedrine, phenol, and sulfamerazine were examined on three unmodified commercial octadecylsilane chromatographic columns. Based on these results, a general RP-HPLC elution scheme using a mu Bondapak C18 10-micron column, methanol-acetic acid-TEA-water mobile phases, and an ultraviolet detector was developed for more than 150 drugs of pharmaceutical interest. The proposed method was applied to the separation of groups of chemically or pharmacologically related drugs that included sympathomimetic amines, antihistamines, phenothiazines, local anesthetics, Cinchona and tropane alkaloids, xanthines, sulfonamides, and steroids. In addition, paired-ion drugs such as physostigmine salicylate and combinations of ascorbic acid, benzoic acid, salicylic acid, pamoic acid, and 8-chlorotheophylline with various basic moieties were readily and effectively resolved into their ionic components using almost identical RP-HPLC conditions.