Metabolism of tramadol, 1-(m-methyoxyphenyl)-2-(dimethyllamminomethyl)-cyclohexan-1-ol, in man was investigated using urine of healthy male volunteers. The drug was administered orally and the urine was extracted and analysed by gas chromatography. Tramadol and two of its metabolites were detected in urine. The major metabolic pathways were O- and N- demethylation and a combination of these metabolic steps. Tramadol was excreted mainly unchanged, about 96%. Thus, biotransformation was not significant in the elimination of the drug from the body.