Knowledge of variation in the reaction of the skin to tuberculin is of importance to the clinician and to the immunologist. The former is interested in several questions, all of which might be answered by a solution of these two: 1. Is a positive skin reaction an absolute indication of tuberculous infection? 2. Is there ever absence of the skin reaction in cases of tuberculosis? Intimately associated with the problem is the effect on tuberculin allergy of advanced or rapidly progressing forms of tuberculosis and the influence of nonspecific factors. It is commonly stated that the skin reaction may become negative in terminal tuberculous conditions such as miliary tuberculosis or tuberculous meningitis. Our own experience and a study of that of others lead us to the conclusion that such a depression in allergy seldom occurs and that the obtaining of a positive skin reaction is mainly a question of dosage.