The mechanism by which Helicobacter pylori associates with the development of upper gastrointestinal diseases is still not well understood. Toxic metabolites of H. pylori are discussed as possible factors. We were interested to investigate, whether biogenic amines might be involved. Ten monocultures of H. pylori from the antrum of patients with H. pylori associated diseases were analyzed for the content of the biogenic amine histamine. The bacteria were isolated on Columbia blood agar with Skirrow's supplement in a microaerophilic environment. After three passages onto fresh agar plates the bacteria were harvested in their sonicated suspensions analyzed by reversed-phase high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). From the HPLC analysis, histamine was found in six cultures. Analysis with GC-MS, however, revealed the presence of histamine in all the cultures (0.1-1.63 nmol histamine/10(8) bacteria). Additionally to histamine, all cultures were found to contain spermidine in concentrations of 0.010-7.912 nmol/10(8) bacteria. It is discussed that histamine produced by H. pylori may be involved in the pathogenesis of H. pylori associated gastrointestinal diseases.