To study the relationship between presence of gastrointestinal allergic manifestations in breast-fed infants and presence of IgE against Schistosoma mansoni antigens, sixty breast-fed infants of S. mansoni infected mothers were selected. Of them, thirty infants were suffering from manifestations of gastrointestinal allergy (patients) and the other thirty were not suffering from such manifestations (controls). Levels of IgE against S. mansoni adult worm antigen (AWA), soluble egg antigen (SEA) and cercarial antigen (CA) were determined, by ELISA, in sera of these infants. There was significant association between presence of allergic manifestations and presence of IgE against AWA (P = 0.018), SEA (P < 0.001) and CA (P = 0.002). Also, concentration of IgE against AWA was significantly higher in patients group than the control group (P = 0.024). IgE against AWA showed significant negative correlation with haemoglobin concentration (P = 0.009) and serum albumin level (P = 021) and significant positive correlation with absolute eosinophilic count (P = 0.005). Also, IgE against CA showed significant negative correlation with haemoglobin concentration (p = 0.047) and serum albumin level (0 = 0.036). It was concluded that gastrointestinal allergy in breast-fed infants of S. mansoni infected mothers may be due to hypersensitivity of Schistosoma mansoni antigens present in mothers' milk. Schistosoma mansoni should be investigated and treated in mothers from endemic localities when their breast-fed infants are suffering from manifestations suggestive of gastrointestinal allergy.