The frequency of sludge and gallstone formation in CCK-1R(-/-) mice fed OA-2 at 6 months of age (5 of 18 mice) was significantly higher than that of those fed CRF-1 (0 of 20 mice)(χ2 = 6.397, p = 0.011), but this frequency in wild-type mice (3 of 22 mice) was not significantly different from the corresponding value (0 of 8 mice) of those fed CRF-1 (χ2 = 1.212, p = 0.271). This evidence concerns the gene CRHR1 and gallstones.