There were 19,419 deliveries at Wilford Hall USAF Medical Center from 1970 through 1981. Of these, 1847 (9.5%) were by primary cesarean section and 800 (4%) by repeat operations. The most common indications for cesarean section (dystocia, breech presentation, repeat operation, and fetal distress) remained the same during this period. However, within these four indications and also between the three time periods of 1970 to 1973, 1974 to 1977, and 1978 to 1981, significant trends were apparent. From the periods of 1970 to 1973 through 1974 to 1977, the primary rate increased from 5.6% to 12.8% (P<.0001). Dystocia (P<.0001), breech presentation (P<.0001), and fetal distress (P<.0001) were responsible for this increase. However, from 1974 to 1977 through 1978 to 1981, the primary rate decreased to 9.6% (P<.0001). This was related to significantly decreased rates for dystocia (P<.0001) and fetal distress (P<.0001). This decrease was temporally related to an initiation of various means to decrease the authors' overall cesarean section rate that approached 20% in 1976. © 1984 by The American College of Obstetricians and Gynecologists.