Catechin is a flavonoid present in fruits, wine and cocoa products. Most foods contain the (+)-enantiomer of catechin but chocolate mainly contains (-)-catechin, in addition to its major flavanol, (-)-epicatechin. Previous studies have shown poor bioavailability of catechin when consumed in chocolate. We compared the absorption of (-) and (+)-catechin after in situ perfusion of 10, 30 or 50 μmol/l of each catechin enantiomer in the jejunum and ileum in the rat. We also assayed 23 samples of chocolate for (+) and (-)-catechin. Samples were analyzed using HPLC with a Cyclobond I-2000 RSP chiral column. At all concentrations studied, the intestinal absorption of (-)-catechin was lower than the intestinal absorption of (+)-catechin (p <0.01). Plasma concentrations of (-)-catechin were significantly reduced compared to (+)-catechin (p <0.05). The mean concentration of (-)-catechin in chocolate was 218 ±126 mg/kg compared to 25 ±15 mg/kg (+)-catechin. Our findings provide an explanation for the poor bioavailability of catechin when consumed in chocolate or other cocoa containing products.