Steroids are widely used for the treatment of leprosy reactions. The effectiveness of steroid treatment is variable, with only 60% of patients regaining nerve function. Sequential skin biopsy specimens, obtained from 15 patients with type 1 (reversal) reactions, have been studied to document the cytokine profile and cellularity of the lesions. All of the patients were placed on a standard course of steroids after the first biopsy. Subsequent biopsies were performed seven, 28 and 180 days later. The specimens were stained for interferon-gamma (IFN gamma), interleukin-12 (IL-12) and inducible nitric oxide synthase (iNOS). After the first biopsy, all patients were placed on a standard reducing course of steroids beginning at 30 mg daily. By day 7, treatment with prednisolone showed little effect on the cellularity and cytokine profiles. However, by day 28, significant decreases of IFN-gamma, IL-12 and iNOS were found for most patients. Some patients maintained cytokine production at day 28 and even at day 180. These data illustrate the strong Th1 profile of type 1 reactional lesions, the relatively slow response to therapy, and the continuing activity after treatment with steroids for 180 days. The variation of individual responses emphasizes their importance. Additional prospective studies will be required to determine whether patients with high intra-lesional levels of cytokine are at risk of recurrent reactions. The need for studies both of different glucocorticoids and of other non-steroidal immunosuppressants for the treatment of reactions is discussed.