A model is described for the induction in the rat of varying degrees of stable uremia using controlled resection of renal tissue. Three degrees of uremia have been attained: ‘mild’ – blood urea 40–80 mg/100 ml (6.68–13.36 mmol/l); ‘moderate’ – blood urea 100–200 mg/l00 ml (16.7–33.4 mmol/l), and ‘severe’ – blood urea greater than 200 mg/100 ml ( > 33.4 mmol/l). Mild uremia was produced by unilateral nephrectomy; moderate uremia required the resection of 80 ± 2% of the total renal mass, and severe uremia was produced by 88 ± 2% nephrectomy. A sham-operative procedure provided an appropriate control for the model. Evaluation of the model has been carried out using analyses of renal function (GFR, concentrating capacity), blood biochemistry, hematological parameters and histological examination. The ability to induce a standardized, stable uremia at predetermined levels, uncomplicated by the administration of nephrotoxic material, represents an advance on existing methods for producing