Localized scleroderma has been shown to be accompanied by various immunologic abnormalities. To obtain functional information on activated CD4+ or CD8+ T cells, we studied the levels of soluble CD4 (sCD4) and soluble CD8 (sCD8) in serum from patients with localized scleroderma. Serum samples were examined by enzyme-linked immunosorbent assay. The samples were obtained from 49 patients in the following three subgroups: 15 patients with generalized morphea, 22 with linear scleroderma, and 12 with morphea. The levels of sCD4 and sCD8 were significantly elevated in patients with generalized morphea. Furthermore, these patients showed significantly higher levels of sCD4 than those with systemic sclerosis (SSc). The frequency of positivity for IgG anti-single-stranded DNA (ssDNA) antibody was significantly higher in localized scleroderma patients with elevated sCD4 levels than in patients with normal sCD4 levels. The frequency of positivity for antinuclear antibodies, IgM antihistone antibodies, IgG anti-ssDNA antibody and rheumatoid factor, and elevated sCD23 levels were significantly higher in localized scleroderma patients with elevated sCD8 levels than in patients with normal sCD8 levels. Our findings suggest that both CD4+ and CD8+ T cells are activated in vivo in generalized morphea and that the immunologic events in generalized morphea are different from those in SSc.