Following oral administration of (+)-catechin and 3-O-methyl-(+)-catechin to human volunteers the major urinary metabolites were shown to be the glucuronides of 3'-O-methyl-(+)-catechin respectively. Isolations from urine and from synthetic products have been carried out by semi-preparative high performance liquid chromatography; definitive elucidations of structures have been carried out by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy.