An isocratic reversed-phase liquid chromatographic assay for tyramine has been developed. The method is based on the reaction of tyramine with 4-chloro-7-nitrobenzofurazan and measurement of the absorbance at 458 nm after chromatographic separation on a C-18 column. Optimum reaction conditions were investigated. A linear relationship was found between absorbance and concentration over the range 25-300 ng per 10 mul of tyramine. The method was applied to the determination of tyramine in cheese. The cheese sample was homogenized with 5% (w/v) HClO4 extracted with ethyl acetate-acetone (2:1) and chromatographed on high performance liquid chromatography (HPLC) after derivatization reaction with NBD-Cl. The determination limit was 25 mug/g cheese. The mean recovery of tyramine from cheese was 98.0%. (C) 2003 Elsevier Science B.V. All rights reserved.