Graft antiglomerular basement membrane nephritis in patients with Alport's syndrome (AS) is a unique complication related to the glomerular basement membrane (GBM) abnormality characteristic of the disease. Its prevalence and clinical significance however remain unknown. We used strict criteria of AS to select 30 patients (26 men, 4 women), aged 17 to 44 years (m: 27) in whom 35 grafts (30 first, 5 second) had been performed at our center between 1968 and 1988. Patient and graft survival were, respectively, 96 and 75% at 5 years, 77 and 42% at 10 years. Graft survival and function, as well as the incidence of rejection episodes in the AS group were not different from those of a control group without AS, matched for age, sex, graft origin, and immunosuppressive regimen. Fifteen grafts were examined by immunofluorescence at least 3 months after TP: linear IgG deposits along GBM were present in 5 cases in the absence of signs of crescentic glomerulonephritis. Circulating anti-GBM antibodies detected in one of these cases 8 months post-TP had disappeared 24 months later. The presence of linear IgG did not seem to influence graft survival and function. We conclude: (1) the overall outcome of TP in AS patients does not differ from a control group without AS; (2) appearance of linear glomerular IgG is frequent but is not necessarily associated with a poor graft outcome; (3) the course of de novo graft anti-GBM disease may be benign; and (4) the aggressivity of the disease could be determined by the degree of immunosuppression and/or by the specificity of the anti-GBM antibodies.