This study is based on the results of investigations with the 19S(IgM)-FTA-ABS in serum samples of more than 10,000 patients with treated or untreated syphilis. On the basis of the findings several experiences concerning the technique of the test as well as the possibilities of biological or technical errors are reported. Furthermore, the interpretation of test results is discussed. It is shown that in many cases a differentiation between sufficiently treated and those patients is possible who need specific treatment. Finally the indications for preparing the test are mentioned. It is concluded that at the present time the performance of the 19S(IgM)-FTA-ABS test should be restricted to specialized laboratories.