We conducted a retrospective study of patients with culture-confirmed multidrug-resistant tuberculosis (MDR-TB) at Bronx-Lebanon Hospital Center (South Bronx, NY) to determine what factors affected clinical and microbiological responses and survival. For the 38 patients with MDR-TB, reporting of first-line drug susceptibilities was relatively rapid (median time, 30 days). Thirty-four patients (89%) were infected with human immunodeficiency virus (HIV), and initial and overall response rates were 59% and 50%, respectively; the median survival was 315 days; and 50% of these patients died of tuberculosis. Bivariate analysis revealed that the following factors had a positive impact on response and survival: receiving > or = 2 consecutive weeks of appropriate therapy with at least two drugs to which the isolate was susceptible in vitro; starting appropriate therapy within 4 weeks of the diagnosis; and having tuberculosis that was limited to the lungs. Multivariate analysis revealed that the only variable associated with response was receipt of appropriate therapy for > or = 2 consecutive weeks. In contrast to findings in the published literature, our results indicate the outcome of MDR-TB can be improved, particularly for severely immunosuppressed HIV-infected patients. Rapid reporting of susceptibilities and prompt initiation and continuation of appropriate antituberculous therapy improved response and survival.