A high-speed liquid chromatographic method was applied to the analysis of nucleic acid bases in photographic gelatins by a cation exchange resin. The retention time and resolution of five nucleic acid bases were investigated by the eluent conditions, such as concentration, pH, flow rate and column temperature. The sample photographic gelatin was hydrolyzed with hydrochloric acid. Highly restraining gelatins contained a relatively large amount of these bases, while lowly restraining or inert gelatins contained little of them.