Wassermann, Neisser and Bruck1 introduced to the medical world the complement-fixation test for syphilis in 1906, and since that time it has undergone several modifications in the hope of making it more practicable and more sensitive with greater specificity; but in all of its modifications, the fundamentals of the test are the same. The disadvantages of the complement-fixation test are well known. The number of biologic reagents that enter into the test increase the source of error. The most important ingredient, complement, is not very stable, and if it should deteriorate without restandardization, one might get false reactions. Although this is overcome by the use of proper controls, many serums contain natural antisheep hemolysin which, if not absorbed, may give false negative reactions. Even if all the reagents used were perfectly stable, the many exact manipulations necessary in making the test make it far from fool proof, especially in