Over a 13-year period 42 patients (35 women) with systemic lupus erythematosus and renal disease had a renal biopsy. Renal involvement as the first and only manifestation of systemic lupus erythematosus was common in men. The commonest reason for renal biopsy (23/42) was the finding of proteinuria with or without haematuria. One-half of all patients had diffuse proliferative glomerulonephritis. Twenty-seven patients were treated with both prednisone and azathioprine and 10 with prednisone alone at some stage during follow-up. The renal biopsy findings were useful in assessing the severity of renal involvement and prognosis. A five-year renal survival of 72% was observed. Diffuse proliferative glomerulonephritis with renal insufficiency was associated with a poor prognosis. Those patients who were established on the dialysis/transplant programme became symptom free on no treatment.