1. Oral administration of 3-palmitoyl-(+)-[U-14C]catechin to rats resulted in the excretion of 63% of the dose in urine, 24% in faeces and 7% as 14CO2 in the 17 days following dosing. Persistent levels of 14C were noted in tissues, and 28 days after dosing 3.7% of the dose was present in the animal body. 2. Biliary excretion accounted for 28.2% of the dose in 48h after dosing. The major biliary metabolite was 3'-O-methyl-(+)-catechin glucuronide. These experiments also demonstrated the dependence of 3-palmitoyl-(+)-catechin on the presence of bile in the intestine for absorption. 3. Studies in vitro showed that intestinal micro-organisms were unable to metabolize 3-palmitoyl-(+)-catechin. The compound did, however, undergo deesterification in plasma and also in liver-perfusion studies. In the latter experiments, conjugates of the liberated (+)-catechin were also formed. 4. Urinary metabolites were predominantly (80%) conjugates of (+)-catechin and 3'-O-methyl-(+)-catechin. Ring scission products and 14CO2 were also excreted but not from rats with ligated bile ducts. These metabolites are therefore considered to arise from biliary metabolites not containing the ester linkage.