IgA-glomerulonephritis represents the most frequent glomerulonephritis (GN; 20%) among our patients. In contrast to data from the literature the prognosis is not benign. Renal insufficiency developed in 17 out of 50 investigated patients within 4 to 96 months, 3 of these patients had to undergo dialysis. Eleven of the 17 patients still had a normal renal function at the time of diagnosis. Malignant hypertension was present in 5 patients. An unfavourable course was predictable in cases of male gender, proteinuria, hypertension, age above 30 years, and histological changes indicating glomerulosclerosis, tubular atrophy, interstitial fibrosis and vascular lesions. Increased serum IgA levels, circulating IgA complexes, association with certain HLA-B or -Dr antigens as well as clinical symptoms and signs of haematuria, dysuria and kidney pains were not helpful either for diagnosis or for prognosis. The value of skin biopsy was comparatively small. Positive IgA demonstration was possible in 12 out of 41 cases with IgA-GN, however, also in 4 out of 21 patients with non-IgA-GN. None of 50 probands without renal disease showed IgA. Five out of 7 skin biopsies demonstrated IgA2, one IgA1 and one both IgA1 and IgA2. Increased serum IgA levels were found in a high percentage (21 out of 38 patients). The same applied to circulating IgA-complexes (8 out of 33 patients).