Activation of autoimmune mechanisms has been associated with infection with various parasites. Observations that link autoimmunity and parasitic infections include (1) the presence of pathogenic autoantibodies and autoreactive cytotoxic T cells to heart and nerve cells in mice and in patients with Chagas' disease, (2) the detection of antibodies directed against self antigens of the inner retina in the sera of the patients with onchocerciasis, and (3) the development of complement-mediated hemolytic anemia associated with autoantibodies reacting with triosephosphate isomerase (TPI) in patients with long standing malaria. Parasitic antigens may induce autoimmune activity and immune-mediated damage to self-antigens by several mechanisms including (1) molecular mimicry between host and parasites, (2) induction of pathogenic autoantibodies, (3) polyclonal activation of B cells, (4) and manipulation of the idiotypic network. This chapter discusses the link among parasitic infections, autoimmunity, and autoimmune diseases. The chapter also discusses the association between autoimmunity and diseases like malaria, leishmania, schistosomiasis, and onchocerciasis in detail.