1,25-Dihydroxyvitamin D3 [1,25(OH)2 D3] may be an immunomodulatory drug which could have a role in controlling collagen deposition, and inducing reversal of fibrosis in some tissues. These observations prompted a study of the possible use of this hormone for the treatment of scleroderma. A 35-year-old woman, who had been suffering from localized scleroderma for 2 years, was given oral 1,25(OH)2 D3 for 6 months. The effects of the treatment were evaluated using clinical and physical measurements (skin thickness, extensibility properties of the skin). The evolution of the patient's condition during the 6-month therapy suggests that 1,25(OH)2 D3 is beneficial in localized scleroderma. The mechanisms of action are discussed in relation to the literature, which suggests both immunoregulatory and inhibitory effects on fibroblast growth.