The main patient series consisted of 415 Egyptians attending the Cairo Cancer Institute and comprising 286 bladder cancer, 97 breast cancer, 14 head and neck cancer and 18 gastrointestinal cancer cases. Also included in the study were 36 patients with active schistosomiasis and 89 health controls. Serum IgA, IgG, IgG subclasses, IgE, Schistosoma and Ascaris-specific IgE (RAST) and the acute-phase protein CRP were measured in all, or sub-sets, of the main patient group. The well-established increase in IgE and IgG levels, and the more recently reported increase in the levels of IgG3 and IgG4 subclasses in patients with schistosomiasis, were also found in bilharzial bladder cancer, indicating that humoral immunity persists in cancer-bearing patients. However, the plasma protein profile in bilharzial bladder cancer is further modified by significant increases in the levels of IgA, IgG, IgG1, IgG2 and CRP when compared to levels in patients with Bilharzia in the absence of neoplastic change. Patients with cancers not associated with parasitic infestation also had significant increases in their serum levels of IgG1, IgG2, IgG, IgE and CRP when compared to healthy Egyptian controls, but 41% of these non-bladder cancer patients showed IgE responses to previous parasitic infestations suggesting that any immunological response to cancer would be on the background of a variable non-specific increase of IgE.