Swabs taken from the amniotic surface of the placenta in a series of 120 Caesarean sections were cultured for mycoplasms and bacteria; organisms of possible significance were isolated from 16 patients. In most of the patients, the membranes had been ruptured for more than 12 hr before Caesarean section, and in 10 of them there was pyrexia after the operation. Some of the babies showed evidence of neonatal infection.