The German Collaborative Glomerulonephritis Therapy Study, which celebrated its 10th anniversary in 1996, has collected data on more than 1,000 patients with biopsy-proven glomerulonephritis. 929 patients could be evaluated and 500 were treated according to at least one of various protocols developed for a randomized controlled trial. Current results show that prednisolone is effective in minimal-change nephropathy, and in combination with other immunosuppressants it can reduce proteinuria in individual cases of focal and segmental glomerulosclerosis, membranous glomerulonephritis and nephrotic IgA nephropathy. The majority of tested treatment protocols did not prove to be superior to symptomatic therapy for long-term outcome.