Summary: As a test for latent malaria the complement fixation reaction with any of the antigens described has proven of only limited value. In chronic relapsing vivax malaria an auto-antibody is often associated with relapses and parasitemia and may be detected with normal human stromata. The “soluble” purified vivax antigen does not react with the auto-antibody but appears to indicate a specific malarial response unrelated to the patient's state of immunity. This antigen, as well as gallinaceum antigen, contains substances reactive with Wassermann antibody.