Five insulin-dependent diabetics in the 3rd trimester of pregnancy were first stabilized on morning and evening injections of both short- and long-acting insulin. Blood sugars were determined hourly from 0700 h to 1900 h and then every 2 h from 1900 h to 0700 h. After glycemic control was established, the patients were treated with continuous s.c. insulin infusion via a pump that administers a basal dosage at predetermined intervals and bolus doses preprandially. Mean blood sugar, glycemic excursions and intervals of hypoglycemia and hyperglycemia were calculated after 3-5 days of infusion therapy. The continuous s.c. insulin infusion with the pump did not improve glycemic control in the group as a whole, but in 2 of 5 patients there was a significant decrease in mean blood sugar. A trend towards a decrease in glycemic excursions as well as hypoglycemia and hyperglycemia was also obtained. Three patients were managed with long-term home and in-hospital use of the continuous s.c. insulin infusion pump. It was efficacious and safe in establishing euglycemia. This study of a portable insulin infusion pump affirms its ability to maintain glycemic control and its safety for long-term therapy during pregnancy.