It is well known that ethanol is oxidized to acetaldehyde in the mammalian organism. Whether the symptoms of acute or chronic ethanol ingestion are caused exclusively by ethanol and acetaldehyde remains to be elucidated. Further pharmacodynamitally active substances may be formed in the organism by other metabolic reactions, such as tetrahydroharmane (THH), also known as eleagnin, which is the condensation product of acetaldehyde and tryptamine. In principle the reaction occurs in vivo, since it was demonstrated in man and rat for tryptamine and 5-hydroxytryptamine with formaldehyde yielding tetrahydronorharmane and 6-hydroxytetrahydronorharmane, respectively. Here, the existence of the beta-carbolines THH and harmane in the urine of man and rat is demonstrated.