Self compatibility (SC), which was found to occur only rarely in the normally self-incompatible (SI) hexaploid garden chrysanthemum, Chrysanthemum morifolium Ramat., was studied by making a series of self and cross pollinations in progenies of 3 different SC sources. SC was transmitted without exception in 15 F1 progenies from crosses between SC and SI plants. No maternal effects were noted in 10 F1. progenies from reciprocal crosses between SC and SI plants. Selfing or intercrossing of SC plants did not produce any large, uniformly SC progenies. Initial intercrosses between SC and SI plants suggested that SC might be controlled by a single dominant factor. Further crosses suggested that the inheritance of SC was more complex and could be associated with more than 1 gene or be modified by other genes such as the S-genes. Seed yield following self pollination in some progenies gave evidence of a clear separation into SC and SI classes while in other progenies the separation was not so distinct. The condition of pseudoself-compatibility was evident in progenies derived from selfing SC plants or crossing between SC plants. SC was used to produce large quantities of inbred seed which is now available for producing both I1 and I2 generations. By using SC parents, the combined self and cross compatibility was increased as compared to compatibility in progenies derived from SI-SI matings.