Sixteen patients with localized scleroderma (LS) and 11 with progressive systemic sclerosis (PSS) were studied using non-invasive techniques to determine skin thickness, skin extensibility, transcutaneous PO2 and cutaneous blood flow and were compared with normal controls. LS was characterized by a decreased skin extensibility with thickening of the skin in progressive lesions. There was an increase in the cutaneous microcirculation with a decrease in the PO2. In PSS, there was a decrease in the skin extensibility caused by thickening of the skin, but no change in cutaneous microcirculation or PO2 values. These results indicate that skin thickness and extensibility are the most useful parameters in the study of the progression of LS and PSS.