The rhizomes of Dryopteris species have popularly been used as vermifuge in flatworm infections. The aim of this work was to evaluate the in vitro schistosomicidal activity of some phloroglucinol compounds, obtained from the rhizomes of Dryopteris species, against Schistosoma mansoni adult worms. All worm pairs were dead after 24 h of incubation with aspidin 25 to 100 microM (1), flavaspidic acid 50 and 100 microM (2), methylene-bis-aspidinol 100 microM (3), and desaspidin 25 to 100 microM (4). Worms incubated with 1 (25 to 100 microM) and 2 (50 to 100 microM) showed decrease motor activity with tegumental alterations, while 3 (100 microM) and 4 (10 to 100 microM) showed decrease motor activity without tegumental alterations. Desaspidinol (5) and filicinic acid (6), at the tested concentrations (10 to 100 microM), did not show activity against adult worms of S. mansoni. Praziquantel (10 microM), used as positive control, caused death of the parasites and tegumental alterations without separation of worms. In the groups treated with 100 microM of compounds 1-4, the viability of the adult worms was similar to the positive control group, in which the worms were dead. Also, both the egg productions and the development of eggs produced by the adult worms were inhibited by the incubation with compounds 1-4 (10 and 100 microM) in comparison with the negative control (RPMI 1640 medium). It is suggested that the in vitro schistosomicidal effects of phloroglucinols derivatives 1, 2, 3, and 4 may be related to the inhibition of oxidative phosphorylation pathway in S. mansoni. The present results confirmed the traditional indications of rhizomes from Dryopteris species, which possess phloroglucinol compounds, in the treatment of tapeworm infections.