High-performance liquid chromatography/mass spectrometry (LC/MS) was applied to the forensic discrimination of dishwashing detergents. Each dishwashing detergent, commercialy available in Japan, consists of anionic, nonionic, amphoteric surfactants or a combination of these surfactants. These surfactants were separated on a reversed-phase C18 column with methanol/10 mM ammonium acetate gradient mo