The development of steroid diabetes was studied in a consecutive series of 114 patients receiving a cadaveric renal graft. All were first-time transplantations. For acceptance in the series the graft should have functioned for at least 2 weeks after the transplant operation. The median age of the patients was 52 years. The follow-up period was at least one year. The criterion for a diagnosis of steroid diabetes was an elevated fasting blood glucose concentration of more than 8 mmoles/l. Fifty-two of the patients (46 per cent) developed steroid diabetes. Thirty-four (65 per cent) of them required insulin therapy or peroral anti-diabetic drugs. The mean age of these patients was higher than for those not afflicted by this complication. The first-year mortality was significantly higher, 42 against 13 per cent, respectively (p less than 0.01). The level of significance was not notably affected by correction for age at transplantation. Severe infection was the cause of a large proportion of the deaths in the diabetes group. The findings suggest that the development of steroid diabetes can serve as a warning signal for excessive dosage of corticosteroids, and help to identify patients that are particularly sensitive to immunosuppressive therapy with large doses of steroids.