Localized scleroderma has been reported to be accompanied by immunological abnormalities related to B cells, but little is known about T-cell activation in this disease. In this study, serum levels of interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-6 (IL-6), which are known to be released by activated T cells, were determined using a sensitive enzyme-linked immunosorbent assay in 48 patients with localized scleroderma and 20 with systemic sclerosis, and in 20 healthy control subjects. IL-2, IL-4 and IL-6 were detected in serum from patients with localized scleroderma but not in that from healthy controls. The presence of antihistone antibodies correlated significantly with elevated IL-4 and IL-6 levels. Decreased serum levels of IL-2, IL-4 and IL-6 paralleled improvement in cutaneous sclerosis. Frequent detection of these lymphokines in serum from patients with localized scleroderma reflects T-cell activation in this disorder.