The transforming growth factor beta (TGF-beta) family controls an extremely wide range of biological activities, such as the growth and differentiation of cells, and immunological events against infectious agents. Although TGF-beta homologs appear to be widely present in metazoan animals, studies of parasite-derived molecules are relatively few. Using antibodies against anti-mouse TGF-beta1, -beta2, and -beta3, we show the expression of TGF-beta-like molecules in Schistosoma japonicum cercariae, schistosomula, eggs and adult worms. Intense immunoreactivity was found on the surface of free-living cercarial bodies. In transverse sections of cercariae, the molecules were localized in the tegument and subtegumental cells, and the number and distribution of producing cells significantly differed with each antibody. In the skin-migrating stage, the expression in the tegumental surface gradually decreased and became almost negative within 48 h of exposure. In adult worms and eggs, the reactivity was found in subtegumental cells and in cells of a tubular structure, respectively. In western blot analysis, the detection of conventional TGF-beta molecules failed. The expression of TGF-beta-like molecules was distinctly regulated at each developmental stage.