The inheritance of coumarin in white blossom sweet clover was determined from a study of crosses involving plants of the variety Arctic (containing free coumarin). Pioneer (containing bound coumarin), and coumarin-deficient selections. Both a flurometric and a colorimeter test were used to detect the presence and type of coumarin.Among high-coumarin plants, variation in the amount of coumarin was due to non-heritable causes or genetic factors not detected in this study. The cross of free-coumarin × bound-coumarin plants established that the bound-coumarin character was inherited as a simple recessive. The gene symbol b is proposed for this character. In the crosses of high-coumarin × coumarin-deficient plants the F1 progeny were more or less intermediate in coumarin content and the subsequent F2 established that coumarin production is governed by one partially dominant gene. The symbol Cu is proposed for this gene. The gene B, responsible for the free-coumarin production, expresses itself only in the presence of Cu and is undetectable in a coumarin-deficient plant homozygous for cu. Some atypical unexplained F2 ratios are reported.