We have shown recently that dietary fat content influences the bioavailability of the flavonol quercetin. In the present study, the influence of the fatty acid pattern of dietary fats on the oral bioavailability of quercetin was investigated. Quercetin (30 micromol/kg body weight) was administered to growing pigs (n 6) in test meals consisting either of 200 g of a standard pig diet (2% crude fat) or of the same diet supplemented with 15 g fat/100 g diet using either medium-chain (MCT) or long-chain fatty acid triacylglycerols (LCT). Blood samples were drawn repeatedly over a period of 24 h and analysed by HPLC. In addition, the influence of the different diets on gastric emptying was investigated in rats. In pigs, the bioavailability of quercetin was measured by quantifying its plasma metabolites with an intact flavonol structure. Bioavailability was enhanced by 38% (P<0.05) and 12% (P>0.05) after intake with the MCT and LCT diets, respectively, compared to the standard diet. Maximum plasma concentrations of quercetin were reached significantly later with the MCT diet than with the LCT or the standard diet (P<0.05). No differences in dry matter of the gastric content were observed 60 min after intake of the experimental diets in rats. Thus, administration of quercetin together with a diet containing MCT fat enhances the bioavailability of the flavonol. Absorption of quercetin was delayed significantly with this diet. However, this was probably not due to slower gastric emptying of the MCT diet.