We evaluated the incidence, severity, and duration of reactional states in 139 multibacillary (MB) leprosy patients in the first 2 years after the completion of the 1 year regimen of multidrug therapy (MDT) currently recommended by the World Health Organization (WHO) and compared those findings with 295 MB leprosy patients treated with the same regimen previously recommended for 2 years. During the first year after the completion of 1 year MDT, patients experienced 1 or more reactional states 27% of the time, the vast majority being lepra type 1 reactions (reversal reactions, RR), whereas patients who received 2 year MDT experienced a reactional state during that time period only 8% of the time (P < 0.001). Furthermore, during the first year after the completion of therapy, and during the first 2 years, both the number of reactional states and reversal reactions were significantly (P ≤ 0.004) more frequent, severe, of longer duration, and more commonly associated with neuritis.