The prevalences of the various histopathologic forms of primary glomerular disease (PGD) were evaluated by the retrospective analysis of 206 kidney biopsies performed in a three-year period (september 1990-september 1993) in patients between 14 and 73 years of age (107 men and 99 women). Data were compared with those of a study conducted in 1985-1987, on patients of the same age group. In the present study, primary glomerular diseases showed the following prevalences: focal glomerulosclerosis, 43.2%; membranous GN, 20.4%; membranoproliferative GN, 14.1%; IgA nephropathy, 10.2%; minimal-change disease, 5.3%; mesangioproliferative GN, 2.9%; acute diffuse GN, 1.9%; rapidly progressive GN and proliferative focal segmental GN, 1% each one. Prevalences were similar in both sexes. Primary glomerular diseases were significantly more prevalent in patients with 35 years or less than in those up this age (64.6% vs 34.4%). Nonproliferative primary glomerular diseases were significantly more prevalent than the proliferative forms (68.9% vs 31.1%). The prevalences of the various histopathologic of PGD, with few exceptions, were about similar in the periods 1985-1987 and 1990-1993: the prevalences of focal glomerulosclerosis, membranous GN, IgA nephropathy and mesangioproliferative GN showed no significant differences; the prevalence of membranoproliferative GN increased (6.8% vs 14.1%), but that of type II remained very low (0.5%). Focal glomerulosclerosis was the most prevalent PGD. The prevalence of IgA nephropathy remained low, comparable with the smallest prevalences found in some of the Western countries.