The ILEP nerve function impairment and reaction research programme (INFIR 2) was a group of clinical trials conducted to identify second-line treatments for severe leprosy type 1 reactions (T1R). This paper presents the clinical results of one of these trials in which azathioprine was used in combination with short-course prednisolone to ascertain if the combination was effective in controlling the symptoms and signs of reaction. Forty patients were alternately assigned to a 12-week treatment with either AP (12 weeks azathioprine at 3mg/kg/d plus 8 week reducing course prednisolone starting at 40mg/d) or P (12-week reducing course prednisolone starting at 40mg/d). Evaluation included serial quantitative clinical assessments. The overall frequency of side effects was similar in both groups. Results show that there was no difference in clinical outcome in the AP and P groups and a similar number of patients in each group required extra prednisolone for worsening clinical features. We conclude that a 12-week course of azathioprine at 3mg/kg/day plus an 8 week reducing course of prednisolone starting at 40mg/d is as effective as a 12 week reducing course of prednisolone starting at 40mg/d and that the combination therapy is well-tolerated in severe leprosy T1R patients.