Sera from normal controls from patients with streptococcal diseases, and from other patients whose serum was sent for anti-streptolysin 0 determinations were tested for antistreptolysin 0 (ASO) and anti-DNase B (ADB) antibodies. The Streptozyme test was performed on the same sera. The upper limits of normal in the control population were established as 160 units for ASO and as 240 units for ADB, respectively. The usefulness of the ADB test in addition to the ASO test was confirmed: when both tests were performed elevated titers could be demonstrated in a higher percentage of various streptococcal diseases. With respect to streptococcal infections of the skin the anti-DNase B-test was superior to the ASO test. In this study of the Streptozyme test showed an elevated antibody titer in a lower proportion than the other two tests.