The effects of corticosteroids in varying doses and duration for the treatment of reaction and nerve function impairment (NFI) in leprosy have been studied extensively. However, an optimal dose and duration of steroid when used as a prophylactic agent for NFI is yet to be established. This study was aimed to determine whether addition of low dose steroid for the initial 8 months of multi drug therapy (MDT) can prevent further deterioration of nerve function (DON) in multibacillary leprosy patients. Sixty multibacillary leprosy patients were randomized into two groups and B consisting of 30 patients each. Group A received MDT-MB for 12 months with prednisolone 20 mg/day from the beginning of treatment for 6 months followed by tapering by 5 mg/2 weeks in 7th and 8th month. Group B received MDT-MB alone for 12 months. Nerve function assessment (NFA) using various modalities was done at the beginning (0 month), at the end of 8 months and at the completion of MDT (12 months). The proportion of patients showing DON was significantly higher in group B, while proportion of patients showing improvement was more in group A. This study thus shows all MB cases with or without NFI at registration should receive prophylactic steroid at least for 8 months. Since preventing deformities using; prophylactic steroids in leprosy is an important issue larger randomized control trials using longer duration of low dose steroid witha longer follow up period should be conducted.