Bile acids derived from intestinal bacterial metabolism and transported to the breast in plasma may influence risk of breast cancer. The purpose of the present study was to test the hypothesis that fatty acid chain length and degree of unsaturation differ with regard to their influence on the postprandial release of cholecystokinin (CCK) and the subsequent increase in plasma bile acid concentrations that occur following a meal. A randomized crossover design was used to compare five high-fat test meals (50 g fat) with a low-fat test meal (15 g) on plasma bile acid and CCK concentrations in eighteen healthy premenopausal women. The high-fat meals were enriched in oleate or palmitate, or linoleate or medium-chain triacylglycerols (MCT) or a blend of oleate and long-chain n-3 fatty acids. The postprandial increase in plasma CCK concentration was lower on the MCT meal compared with all meals and was greater following the linoleate compared with the low-fat meal. Plasma bile acid concentrations increased 2-3-fold postprandially but the increase was lower following the MCT meal compared with the other meals and was greater on the linoleate meal compared with the low-fat meal. The postprandial increases in plasma chenodeoxycholic acid concentration showed a trend to rise with increasing unsaturation of the test meal. In conclusion, meals rich in linoleate are a potent stimulus for CCK release and lead to prolonged elevations of plasma bile acids and meals containing MCT inhibit CCK release and the subsequent increase in plasma bile acid concentrations.