Recently antimicrobials of the fluoroquinolone class (pefloxacin and ofloxacin) were found far more effective against Mycobacterium leprae in studies with both mice and patients than dapsone and clofazimine. As multicentre trial participants, we evaluated the therapeutic efficacy, in terms of rate of relapse, of two new multidrug regimens containing ofloxacin, comparing them to 1 year and 2 years of standard WHO-MDT regimen in multibacillary (MB) leprosy patients. A total of 198MB patients were recruited to participate in a randomized, double-blind trial. Among those, 53 patients were treated with 1 year of WHO-MDT (a regimen including dapsone, clofazimine, and rifampin), 55 patients received 1 year of WHO-MDT plus an initial 1 month of daily ofloxacin, 63 patients were treated with 1 month of daily rifampin and daily ofloxacin, whereas 27 were treated with 2 years of WHO-MDT. Patients were regularly monitored for signs of relapse, in at least 7 years follow-up after being released from treatment. Relapse occurred in those treated with 1-month regimen alone at a significant higher rate (P < 0.001): 388%, whereas in the other three regimens that included WHO-MDT it ranged from 0 to 5%. This study found that a short-course treatment for MB patients with rifampicin-ofloxacin combination had a higher failure rate. The addition of one month of daily ofloxacin to 12 months MB WHO-MDT did not increase its efficacy.