Cryopreservation of human embryos has been successfully applied in in vitro fertilization (IVF) and embryo transfer (ET) programs at the National Taiwan University Hospital since 1988. Our preliminary results with 120 frozen-thawed embryos in 31 transfer cycles showed that the survival rate of frozen embryos was 66%. Following transfer, the implantation rate and clinical pregnancy rate were 6.5% and 13%, respectively. Four clinical pregnancies and one preclinical pregnancy following a frozen-thawed embryo transfer were achieved. Two normal male babies have been delivered and another pregnancy is progressing without any problem.* Unfortunately, one pregnancy was terminated due to intrauterine fetal death discovered at the 10th week of gestation; chromosome abnormality (47, XX, +5) of the fetus was found. The single preclinical pregnancy showed an elevation of serum beta-human chorionic gonadotropin levels for three consecutive weeks following ET, but no definite gestational sac was visualized by transvaginal ultrasound.