The mode of presentation of renal disease in 44 patients with essential mixed cryoglobulinaemia (EMC) was: acute renal failure (two patients), acute nephritic syndrome (six patients), nephrotic syndrome (eight patients), proteinuria and/or haematuria (28 patients). Renal biopsy, performed in 35 patients showed proliferative lesions in 33, while only minimal glomerular changes were seen in the remaining two. Immunofluorescence studies showed: IgG (85 per cent), IgA (36 per cent), IgM (90 per cent), C3 (90 per cent), C1q (47 per cent), and C4 (33 per cent) deposits, mainly located in subendothelial position. On electron microscopy, crystalloid structure of deposits and monocyte infiltration of capillary loops were the outstanding feature. The survival rate was 75 per cent at 10 years from the onset of clinical symptoms. Thirty-nine patients were followed for three to 146 months (mean 53.8). Twelve patients died, cardiovascular disease and infection being the commonest cause of death. Thirteen patients showed acute renal failure of acute nephritis syndrome: nine recovered completely, whereas the remaining four died during the acute renal episode. Three patients developed chronic renal failure, but only one period required chronic dialysis. The ominous significance of renal impairment in EMC should therefore be revaluated. The high prevalence of hypertension (28/44 patients) which was refractory to treatment in six, may be important to the clinical outcome.