Rabbit embryos in the two- and four-cell stage were placed in rabbit and bovine serum with and without the addition of 100 mg glucose per 100 ml serum and cultured for 97 hr. Maximum development in culture was to the expanding blastocyst stage. Embryos were transferred to recipient does after 0, 24, 36, 48, 62, 72, 88 and 97 hr in culture. Embryos transferred after 62 hr in culture readily developed into neonates, and one embryo cultured for 88 hr to the blastocyst stage developed into a full-term young. The addition of glucose significantly increased (P<0.005) the number of blastocysts produced in culture.