S. mansoni and F. gigantica GSTs were purified from adult worm homogenates by affinity chromatography. Assessment of both SmGST and FgGST as candidate vaccines was done by comparing vaccinated mice groups challenged with S. mansoni cercariae with control ones in terms of worm load, tissue egg number viability and maturity, and the survival rate of the animals. SmGST 5 ug vaccination generally appeared to confer best protection against homologous challenge followed by FgGST 5 ug while vaccination with both antigens using low doses (2 ug) appeared to have no specific role in decreasing worm load but had significant effects on egg production.