Intraperitoneal absorption of human insulin (crb) and porcine insulin was examined in 9 diabetic patients with renal failure, and on Continuous Ambulatory Peritoneal Dialysis (CAPD). Serial blood sampling was performed to determine the characteristics of insulin absorption and glycaemic control. Four patients received successive equal doses of human and porcine insulins, 2 received different doses and 3 received human insulin only. Glycaemic control was similar after both insulins. Mean insulin levels were consistently higher after human insulin with significant differences at 90, 300 and 360 min. It is concluded that, if required, patients may be transferred from i.p. purified porcine to i.p. human insulin without a change in insulin dose.