Hyperlipidaemia has been previously shown to accelerate various models of renal disease. The present study has evaluated the effects of dietary cholesterol supplementation on functional and structural aspects of experimental diabetic nephropathy. Control and streptozotocin diabetic male Sprague Dawley rats were randomized to receive a normal diet or a high cholesterol (4% cholesterol + 1% cholic acid) diet. After 32 weeks, serum lipids, glycaemic control, urinary albumin excretion and glomerular ultrastructural parameters were evaluated in the 4 groups. Diabetes was associated with increased total cholesterol and triglyceride levels. Cholesterol supplementation increased total and decreased HDL-cholesterol in control and diabetic rats. Diabetes increased albuminuria but cholesterol supplementation did not influence urinary albumin excretion. In diabetic rats, glomerular basement membrane thickness and glomerular volume were increased but cholesterol supplementation did not influence any glomerular ultrastructural parameter. In control rats, increased dietary cholesterol intake led to an increase in blood pressure and glomerular volume. In contrast to other models of renal disease, experimental diabetic nephropathy does not appear to be exacerbated by dietary cholesterol supplementation.