With the resurgence of tuberculosis (TB) disease in the late 1980s and early 1990s in the United States, multidrug-resistant (MDR) TB emerged as a serious challenge to TB control. In response, the Centers for Disease Control and Prevention in 1993 added drug susceptibility test results to the information collected for the national surveillance system to monitor trends in drug resistance.To determine the extent of drug-resistant tuberculosis (TB) in the United States.Descriptive analysis of TB surveillance data.Patients reported to the national TB surveillance system as confirmed TB cases with culture-positive disease from 1993 through 1996 by the 50 states, New York City, and the District of Columbia (DC).Percentage of case patients with culture-positive disease whose isolates are resistant to specific anti-TB drugs.Overall resistance to at least isoniazid was 8.4%; rifampin, 3.0%; both isoniazid and rifampin (ie, MDR TB), 2.2%; pyrazinamide, 3.0%; streptomycin, 6.2%; and ethambutol hydrochloride, 2.2%. Rates of resistance were significantly higher for case patients with a prior TB episode. Among those without prior TB, isoniazid resistance of 4% or more was found in 41 states, New York City, and DC. A total of 1457 MDR TB cases were reported from 42 states, New York City, and DC; however, 38% were reported from New York City. Rates of isoniazid and streptomycin resistance were higher for cases among foreign-born compared with US-born patients [corrected] but rates of rifampin resistance and MDR TB were similar. Among US-born patients, resistance to first-line drugs, particularly rifampin monoresistance, was significantly higher among those with human immunodeficiency virus (HIV) infection.Compared with recent US surveys in 1991 and 1992, isoniazid resistance has remained relatively stable. In addition, the percentage of MDR TB has decreased, although the national trend was significantly influenced by the marked decrease in New York City. Foreign-born and HIV-positive patients and those with prior TB have higher rates of resistance. The widespread extent of isoniazid resistance confirms the need for drug susceptibility testing to guide optimal treatment of patients with culture-positive disease.