The effect of additional oral ofloxacin administration was evaluated in 19 HIV-negative patients with multidrug-resistant tuberculosis (MDR-TB). Their mean duration of illness was 3.6 years. Based on chest roentgenograms, 13 patients had advanced disease and 6 had moderate disease. In addition to 'second-line drugs', patients were treated with oral ofloxacin; high dose 800 mg per day (12 patients), low dose 400 mg per day (2 patients) and intermittent twice a week regimen of 800 mg a day (5 patients). With treatment, there was a significant clinical improvement. Sputum smear conversion occurred in 18 patients (mean duration 15 weeks) and this sputum smear negativity persisted for a mean duration of 7 months. Chest roentgenograms revealed regression of lesions in 18 patients. Reversible side effects were encountered in four patients. Results of present study suggest that additional administration of oral ofloxacin is both effective and safe for the treatment of MDR-TB.