A high-school-based health center instituted a tuberculosis testing and treatment program. Compliance of purified protein derivative (PPD) positive students with isonicotine hydrazine (INH) preventive therapy was compared for two groups of students: those in directly observed preventive therapy (DOPT) and those in traditional therapy. Four hundred thirty six students were tested and 429 returned for a reading: 209 (49 percent) students had a positive PPD test. The rate of positivity did not vary by age, sex, or years in the United States. There was no relationship between bacille Calmette-Guérin (BCG) vaccination and rate of positivity or mean size of induration. The compliance rate for all courses of DOPT was significantly higher (54 percent) than that for traditional therapy (26 percent). The compliance rates for the first and second attempts to complete a course of DOPT was 71 percent. Completion of therapy did not differ by age, sex, or years in the United States. Haitian students completed therapy more often than students from Jamaica. We believe it is effective and efficient to base tuberculosis testing and treatment with DOPT in the school setting.