A 30-year-old Japanese female with Turner's syndrome had become pregnant and delivered a normal male infant by cesarean section. Her menarche was at age 14, and secondary sex characteristics developed normally. She had some features of Turner's syndrome, and cytogenetic studies from peripheral blood lymphocytes and several tissues revealed only 45,XO karyotype without evidence of mosaicism. To our knowledge, she is only the thirteenth case of monosomy X to achieve pregnancy. A review of the literature indicates a high incidence of fetal wastage and increased chromosomal errors in the offspring of women with a 45,XO cell line with or without mosaicism.