In attempting the early detection of glomerular abnormalities in patients with the hepatosplenic form of Schistosoma mansoni infection, the serum concentration of beta 1C/1A globulin was determined in 17 patients without clinical evidence of nephropathy. Renal biopsies were obtained during splenectomy in all of them. The serum levels of beta 1C/1A globulin were below the normal limit in eight patients; of these, two had histological evidence of focal proliferative glomerulonephritis, two others had membranoproliferative glomerulonephritis, and one showed focal sclerosing glomerulonephritis. Of nine patients with normal serum levels of beta 1C/1A globulin, eight had no glomerular abnormalities demonstrated by light microscopy. Determination of the serum concentration of beta 1C/1A globulin proved to be a valuable index for the detection of early glomerulopathy in patients with hepatosplenic schistosomiasis, since a low level correlated well with the histologic demonstration of glomerular involvement by light microscopy.