Studies utilizing glucose-controlled insulin infusion systems were undertaken to more accurately define the glucose and insulin requirements during the first stage of labor induced by oxytocin in 12 insulin-dependent diabetic women in whom normoglycemia had been maintained before delivery. Insulin requirements decreased to zero during active stage 1 labor, while the glucose infusion rate necessary to maintain a blood glucose level of 70 to 90 mg/dl (or 3.9 to 5.0 mmol/liter) was constant at 2.55 mg/kg per minute. The findings were confirmed in 40 additional studies of oxytocin-induced labor. Studies of six women undergoing spontaneous labor and one nonpregnant woman receiving oxytocin confirmed that the decrement in the insulin requirement during stage 1 labor was not influenced by oxytocin infusion. The changes occurred regardless of whether epidural anesthesia was employed. Insulin requirements returned during the second stage of labor. Active stage 1 labor in diabetic women thus appears to be associated with a predictable decrease in the need for insulin and a constant glucose requirement.