Dopamine hydrochloride is reported to be a new mutagen precursor in this study. After treatment with nitrite under acidic conditions, dopamine hydrochloride showed direct-acting mutagenicity on Salmonella typhimurium TA100, TA98 and Escherichia coli WP2uvra. The addition of S9 mix did not affect the mutagenicity of nitrosated dopamine significantly in these three strains. Meanwhile, a comparison of the mutagenicity of nitrosated dopamine with nitrosated tyramine was carried out.