Hypertension is highly prevalent in both types I (87%) and type II (95) uremic diabetics at the time of kidney transplantation. Hypertension was diagnosed a mean of 16.9 yrs in type I, and 2.9 yrs in type II diabetics after the clinical diagnosis of diabetes was made. The majority (81%) of our patients were hypertensive postkidney transplant. Only 13% of hypertensive recipients became normotensive post-transplant. This group had a lower mortality rate (1/8, 12.5%), and all survivors (100%) had good graft function (mean creatinine = 1.6 +/- 0.6, range 0.9 to 2.5 mg/dl). By contrast, recipients who remained hypertensive post-transplantation had a much higher mortality rate (25/54, 48%), and loss of graft function necessitating dialysis occurred frequently (19/54, 35%). Of hypertensive diabetic recipients alive at a mean of 21 mos post-transplant, renal function was worse (mean creatinine = 3.1 +/- 3.0, range 1.0 to 13.7 mg/dl) than in nonhypertensive recipients. We conclude that while renal transplantation may be the treatment of choice in patients with diabetes mellitus, failure to control hypertension negatively biases the ultimate post-transplant course.