Four patients with mansoris Schistosomiasis infection were treated with a new compound - K-7505 (Ronnel) or 0,0 - dimethyl - 0 - (2, 4, 5 - trichlorophenyl) - phosphorothioate, and the therapeutic activity was evaluated by examination of rectal biopsy (oogram), and Hoffmann, Pons and Janer technique 14 days after the treatment. The author concluded that the drug does not have action against Schistosoma mansoni