We have carried out a comparative study on differences in operative obstetrical practice during the 1970s and 1980s, in Norway, Scotland and the United States of America. It was based on information from official sources in each country. We compared rates of cesarean section (CS) and operative vaginal delivery according to maternal age, parity and gestational age at delivery, birthweight, fetal presentation, and other characteristics of the child, indications for operative delivery, and hospital size and teaching status. While all three countries had rising CS rates, the Scottish rates, which lay between those of the U.S.A. and Norway, rose more slowly than in the latter. In 1985, the rates were 22.8% in the U.S.A., 13.5% in Scotland and 12.0% in Norway. Use of forceps and vacuum extractor declined in the U.S.A. and Scotland, but increased in Norway. CS rates in mothers aged 35 and over were uniformly high in 1970 and rose relatively little. Specific CS rates for very low birthweight children, breech presentation and twins rose to 30-50% in all three countries with some national trend differences. Rate ratios of operative delivery between large and small hospitals fell from about 2-3 in the 1970s to approximately 1.5 in 1985, least markedly in Scotland. The impact of previous CS as an indication for CS cannot be resolved because of notification and recording differences.