Patients with scleroderma-like lesions secondary to metastatic secreting carcinoid tumors are different in several ways from patients with progressive systemic sclerosis. Scleroderma resulting from a carcinoid does not have an acrosclerotic distribution but develops first in dependent regions of the body following pronounced pitting edema. Raynaud's phenomenon is absent. Results of serological tests are negative. The typical internal organ changes of systemic sclerosis are not seen. Differences in end-organ (skin) response to exogenous serotonin creatinine sulfate suggest metabolic differences as well. It is probable that scleroderma arises by a different mechanism when associated with the carcinoid syndrome than when seen independently, and that this mechanism involves capillary permeability and tissue edema induced by serotonin or other active tumor metabolites.