Thirty-nine cases of hepatosplenic schistosomiasis associated with renal disease are included. They were investigated for renal function, serum and urinary immunoglobulins, some serological tests, and bacteriological studies for evidence of associated salmonellosis. Renal biopsy was obtained from 23 subjects and studied by light microscopy. It was possible to distinguish two groups of cases "salmonella-negative" and "salmonella-positive". The former group was characterized by marked glomerular lesions, mainly membrano-proliferative, in different phases of evolution. Salmonella-positive cases were categorized into those with clinical, laboratory and histological evidence of interstitial nephropathy (six cases), that seems to result from salmonella pyelonephritis; and those with overt glomerular lesions (17 cases). The latter group differed from salmonella-negative cases in having mainly proliferative glomerular lesions with minimal or no basement membrane thickening; the lesions were diffuse and appeared in the same stage of evolution. The possible relation of schistosomiasis and associated salmonellosis to the pathogenesis of these lesions is discussed, suggesting an immunological basis for the glomerular injury and outlining the possible significance of hepatic fibrosis.