Many adolescents who are prescribed therapy for tuberculosis (TB) infection fail to complete it. This article presents the results of a demographic and epidemiological assessment of TB treatment completion in adolescent populations using (a) surveillance data from the Los Angeles Health County Department and (b) a prospective/retrospective medical chart review from targeted clinics. Patients who did not complete the 6-month recommended medical treatment for latent tuberculosis therapy (LTBI) averaged 13 weeks in care. Younger age (OR = 1.15; 95% CI 1.03-1.29), birth in the United States (OR = 1.92; 95% CI 1.14-3.22, compared to Mexico), and Asian ethnicity were associated with completion of care. In multiple logistic regression analysis, age (OR = .88; 95% CI .78-.98) and Latino ethnicity (OR = .53; 95% CI .29-.95) remained significant predictors of completion of treatment. These findings indicate the need for age-specific educational reinforcement and cultural differentials in completing care for LTBI.