A 66-year old male with severe hyperglycaemia due to previously uncontrolled diabetes mellitus was also suffering from arteriosclerosis obliterans and diabetic nephropathy. The patient was treated with 16 IU/day insulin zinc suspension. In addition, an intravenous infusion of 80 micrograms/day prostaglandin E1 was given for 28 days in an attempt to improve the arteriosclerosis obliterans and diabetic nephropathy. Treatment resulted in a reduction in fasting blood glucose but no decline in urinary protein. Prostaglandin E1 treatment, however, produced an improvement in renal haemodynamics assessed by renography.