[3H] Lorcainide hydrochloride was administered orally to healthy male volunteers. About 97% of the total radioactivity was excreted in the urine and faeces within four days of its administration. The metabolites were purified by adsorption chromatography, liquid-liquid extraction, thin layer chromatography or by gas chromatography-mass spectrometry after silylation of the samples. When there was a sufficient amount available, the samples were submitted to a nuclear magnetic resonance analysis. The results were confirmed by comparison of spectral data obtained from the reference compounds. The major metabolites of lorcainide were formed by aromatic hydroxylation, O-methylation and oxidative N-dealkylation. The urinary phenolic metabolites were present both as free aglycons and conjugates.