The cesarean section rate has been rising in California since 1965. In this article, we describe the trend in cesarean section rates in California from 1960 to 1975 in relation to maternal and infant variables. Approximately proportionate increases in cesarean section rates by infant birth weight and maternal race were found. Cesarean section rates for women under 20 years of age and for those of first parity have risen proportionately more than rates for other age and parity groups. We also found that cesarean section rates for births at gestational age's exceeding 42 weeks have risen proportionately more than rates for births at other gestational ages. Maternal mortality ratios associated with cesarean section were twice those associated with noncesarean births for the years 1973, 1974, and 1975. Possible explanations of the current cesarean section rate include an increase in indications for the procedure, use of the fetal monitor, and the current medical-legal climate. The potential problems that cesarean section may create for the mother and infant are higher rates of iatrogenic prematurity and respiratory distress and of maternal morbidity and mortality.