The persistence of tuberculosis bacilli in patients who are cured, thus causing recurrence, is an important issue. This case-control study investigated individual and institutional risk factors for relapse by analyzing independent variables related to the patient, the use of antituberculosis drugs, and the service delivered at health care institutions; 56 cases and 105 controls were interviewed. Recurrence was defined as a new tuberculosis episode after the patient had been successfully treated. Controls were selected from among patients who were treated and cured of pulmonary tuberculosis and who did not experience a relapse. Regression models were proposed to control confounding factors or effect modifiers. The variables identified as risk factors for relapse were those related to erratic patient behavior (missing medical appointments and therefore not picking up the medication, not taking the medication, taking the wrong dosage), age, and stress from life events; adverse reactions to antituberculosis drugs; and problems in the organization of health care services that resulted in patients receiving insufficient dosages or amounts of antituberculosis drugs. Receiving information regarding treatment duration provided protection against recurrence. The knowledge regarding these risk factors should result in more intensive follow-up and in more use of directly observed treatment of tuberculosis in order to prevent relapse.7232-41