In a study of 48 patients with systemic sclerosis (SSc). elevated serum levels of soluble interleukin 2 receptor (IL-2R), interleukin 2 (IL-2) and neopterin (indicators of lymphocyte/monocyte activation) were noted in 100, 44 and 40% of early untreated patients with SSc (11 diffuse, 5 Limited). Levels of IL-2R, but not IL-2 or neopterin, were lower in patients with longer duration of disease and possibly with chlorambucil therapy. Pharmacologic alterations of markers of humoral or cell mediated immunity may not be an accurate reflection of clinical efficacy of chlorambucil.