Information on 934 never married mothers (Single) were compared with 301 who were widowed, divorced or separated (Once-married) and 15 225 who were married at the time of delivery and were part of the 1970 British Births Survey. Once the maternal age and parity differences had been taken into account the major findings concerned the mothers' health behaviour and the obstetric care they received. Single and Once-married mothers were markedly less likely than the Married group to have used contraceptives in the 18 months before conception, to know accurately the date of the last menstrual period, to commence antenatal care before the third trimester, and to attend antenatal or parentcraft classes. Both groups were more likely to smoke, the Once-married group having an especially high rate of heavy smokers. Single mothers were more likely to be anaemic during pregnancy and the Once-married to have a history of bleeding. Both groups were more likely to be delivered in a consultant unit. Relatively high proportions of Single and Once-married mothers had delivered without any pain relief.