Skin to lung migration of Schistosoma mansoni Sambon, 1907 - (75 Se) - selenomethionine-labeled cercariae was tracked by tissue autoradiography on days 1, 4, 6, 8 after challenge, in rabbits immunized with a S. mansoni derived saline extract. Either in vaccinated animals or in those of the control unprimed group, the peak of skin schistosomula occurs 24hs after infection. Comparison between peaks of lungs migrating larvae showed that, in control animals, the increase of worm burden in this site, is detected on the 6th day post-infection, differing from immunized rabbits, in which this peak occurs on day 4, when skin and lungs counts are still equivalent, decreasing gradually, showing a different pattern of the S. mansoni migration and suggesting that main parasite attrition occurs during the late skin and early lung phases in the immunized group.