To study the relationship between micronutrient malnutrition and schistosomiasis mansoni, a cross-sectional study was undertaken involving 421 schoolchildren (mean age 12.6 years; 333 from schistosomiasis mansoni-endemic villages (Workemado and Sille) and 88 non-endemic controls from Sheno). Prevalence of schistosomiasis mansoni infection in Workemado and Sille was comparable (90.6% versus 95%, respectively), and prevalence of PPF in Workemado was significantly higher than in Sille (7.0% versus 0.6%, P < 0.001). Compared with non-endemic controls, serum retinol concentrations were significantly lower and hydroperoxides were significantly higher in subjects from schistosomiasis mansoni-endemic areas. Furthermore, serum alpha-tocopherol concentrations in subjects from an area with high prevalence of PPF were significantly reduced while the concentrations in subjects from an area with low prevalence of PPF were comparable to the levels found in non-endemic healthy controls. In conclusion, micronutrient malnutrition and oxidative stress are associated with Schistosoma mansoni infection and levels of schistosomal PPF.