PATIENTS with therapeutically resistant acne vulgaris are still commonly seen. Occasional patients fail to show adequate response in spite of intensive treatment with dietary restrictions, local agents, removal of infectious foci, roentgen therapy, comedone expression, endocrinologic agents, vaccine therapy, and other acceptable remedies. Clinically, it has been shown that the administration of one of the sulfonamides or an antibiotic may cause decided improvement in some instances of pustular acne.1 The decision as to which of these therapeutic agents the clinician should try first becomes rather significant. In an attempt to answer this problem, two of the methods for carrying out in vitro sensitivity studies have been utilized comparatively in this investigation. One of these is designated the paper disc method and technically is easily performed. The other method consists of tube serial dilution tests and involves considerably more time and effort in its execution. Only patients with the pustular