Between April 1975 and March 2005, 4,436 cases of histologically proven glomerulonephritis (GN) were diagnosed by the same team at the Kidney Unit of Charles Nicolle Hospital in Tunis. Respectively 1,510, 1,419 and 1,509 cases were diagnosed in 1975-1985, 1985-1995, and 1995-2005. We compared trends in the incidence rates of the different types of GN and those of Tunisian indicators of health, social and economic status. The following differences were found between 1975-1985 and 1995-2005:--As a proportion of all cases of GN, the frequency of amyloidosis fell from 12,6 % to 6,5 % (p < 0,0001). The 444 cases of amyloidosis observed during the study period were of type AA in 87 % of cases, and were related to chronic infectious diseases in 239 cases (54 %; pulmonary tuberculosis in 114 cases). The frequency of tuberculosis-associated amyloidosis fell during the study period, in parallel with the reduction in the incidence of tuberculosis in the Tunisian population (48,7 cases/100,000 inhabitants in 1983 to 20,17 in 2004). Lupus nephritis accounted for 7.7 % of all cases of GN diagnosed in 1975-1985, compared to 13 % in 1995-2005 (p < 0,00001). Increased exposure to sunlight and use of cosmetics could be involved in this increase.--The incidence of both proliferative endocapillary and membranoproliferative GN (as a proportion of all cases of GN) fell between 1975-1985 and 1995-2005, from 15,9 % and 21,6 % to 6,9 % and 7,7 %, respectively (p < 0,0001). This matched a drop in the incidence of acute rheumatic fever in the Tunisian population, from 7,26/100,000 inhabitants in 1984 to 0,83 in 2004, probably as a result of public health measures and widespread use of antibiotics. The incidence of membranous GN increased from 11,1 to 17,7 % in adults (p < 0,001) whereas it fell from 10,1 to 4,6 % in children (p < 0,01), possibly as a result of a nationwide HBV vaccination program launched in 1995. The incidence of IgA nephropathy increased from 0,9 to 12,9 % in adults (p < 0,0001) and from 0,3 % to 18,4 % in children, but remained relatively stable in elderly adults. This study, conducted in a single center, by the same team, and using the same renal biopsy practices, confirms that the control of infectious diseases in Tunisia has led to a substantial regression of proliferative endocapillary and membranoproliferative GN and renal amyloidosis. Environmental factors, such as the adoption of western lifestyles, could explain the increase in lupus and IgA nephropathies.