The optimal duration of tuberculosis treatment for persons infected with human immunodeficiency virus (HIV) has been debated. A cohort of 4571 culture-positive drug-susceptible patients who received > or =24 weeks of standard 4-drug tuberculosis treatment were assessed to determine the incidence of tuberculosis relapse. Tuberculosis "recurrence" was defined as having a positive culture < 30 days after the last treatment date and "relapse" as having a positive culture > or =30 days after the last treatment. Patients infected with HIV were more likely than those who were uninfected to have recurrence or relapse (2.0 vs. 0.4 per 100 person-years, P< .001). Patients infected with HIV who received < or =36 weeks of treatment were more likely than those who received > 36 weeks to have a recurrence (7.9% vs. 1.4%, P< .001). Clinicians should be aware of the possibility of recurrence of tuberculosis 6-9 months after the start of treatment. Sputum evaluation to ensure cure or assessment 3 months after completion of treatment should be performed among persons infected with HIV who receive the shorter regimen.