Hyperlipoproteinemia is common in recipients of renal allografts. In this study, serum lipids and some possible contributing factors--weight gain, weight relative to ideal body weight, daily dose of prednisone, serum creatinine, 24-hour urinary protein, and diabetes mellitus--were assessed in 100 patients. At the end of the first year after transplantation, 57 of the 100 patients had total serum cholesterol concentrations of 240 mg/dl or more--40 of 75 patients without diabetes and 17 of 25 with diabetes. The mean values for weight gain (11.2 kg) and actual weight relative to ideal body weight (19.4 kg) were significantly greater (P = 0.029 and P = 0.01, respectively) in the subgroup of patients without diabetes who had total serum cholesterol values of 240 mg/dl or more at 1 year after transplantation than in those with values of less than 240 mg/dl. The daily dose of prednisone and the serum creatinine levels were similar in these two subgroups. The 24-hour urinary protein measurements were greater at 1 month than at 1 year in both patients with and those without diabetes. Perhaps the initial dietary advice for patients who have undergone renal transplantation should emphasize control of total caloric intake; subsequently, intake of cholesterol and fat can be modified in those patients who have persistent hyperlipoproteinemia.