We have added insulin to peritoneal dialysis fluid in three uraemic diabetic patients. The hyperglycaemia and pronounced fluctuations in blood glucose which complicate peritoneal dialysis in diabetic subjects have not occurred with this technique. Studies with (131)I-labelled insulin showed that less than 5% of the intraperitoneally administered insulin was absorbed during a one-hour exchange. While the physiology of the procedure needs further evaluation, this procedure has reduced the morbidity of peritoneal dialysis in diabetic patients and made its management easier.