In a prospective study, 1156 blood specimens collected from hospitalized febrile obstetrical-gynecologic patients and neonates with suspected sepsis, were inoculated into a conventional biphasic culture medium, Castaneda S and cultures incubated aerobically. 15-24 h later the broth cultures were subcultured to specific media for detection of mycoplasmas. Genital mycoplasmas were isolated in 15 samples (taken from 8 women) and in 2 from 1 neonate. Mycoplasmas and members of the family Enterobacteriaceae were the most frequent significant bacteria isolated from adult specimens. Mycoplasma isolations were associated with either postpartum or postabortum febrile infections in women. Four of the neonates, whose mothers were infected, showed respiratory distress at birth; 1 of them had mycoplasmas in the blood. All febrile states in obstetrical or gynecological patients, and in neonates, should routinely lead to blood cultures for detection of mycoplasmas and ureaplasmas.