Electromyographic findings were studied in 32 women and 7 men with progressive systemic sclerosis. Among the 14 patients in group 1, 7 had the CREST syndrome in an early stage while the 14 patients in group 2 had advanced CREST-type lesions. The 18 patients in group 3 had diffuse scleroderma with extensive visceral involvement. In all groups, the mean duration of single potentials was reduced and the percent of polyphasic potentials was above normal in groups 2 and 3. Distal muscles were more involved in group 1, and proximal muscles in group 2. In group 3, involvement of various muscles was nearly equal. Electromyographic changes correlated with the clinical condition of the patients. Overall, the findings in this study are similar to findings from other laboratories.