Isolated glomerulonephritis with mesangial IgA deposits was the most common single finding encountered in a large biopsy series in an Australian community and was found in 50 patients, 18% of those presenting for the investigation of primary glomerular disease. A uniform histopathological picture of mesangial enlargement, with or without focal and segmental features was present. A tendency to progression was suggested by the frequent presence of glomerulosclerosis, interstitial scarring and vascular hyalinization. Because of the uniform histological immunofluorescence and ultrastructural appearances, the term IgA nephropathy has been used for this condition. The clinical picture, however, was heterogenous. Presenting symptoms included macroscopic hematuria (34%), proteinuria (32%) acute nephritis (10%), nephrotic syndrome (6%), malignant hypertension (8%), acute renal failure (6%) and chronic renal failure (4%). There was a striking correlation of increased blood pressure and decreased renal function with increasing age. While the period of follow-up was too short to assess individual patient data, a gradual and progressive decrease in renal function over several decades is suspected in patients with this condition.