Interleukin-2 (IL-2) is a lymphokine produced by activated T cells and its receptor (IL-2R) is expressed on T cells; one of the IL-2R components can be measured as a soluble serum protein (sIL-2R). Levels of sIL-2R were measured as a sign of T cell activation in serum of 12 patients suffering from alopecia areata (totalis or universalis) and in a group of healthy control subjects. An enzyme-linked immunosorbent assay was used to determine the levels of sIL-2R in blood samples drawn during both the active and resting phase of the disease. In patients with alopecia areata in active phase the sIL-2R concentrations were significantly higher than in stable phase and in controls. The biologic role of sIL-2R is still unknown, but one could speculate that T lymphocyte activation with subsequent secretion of IL-2 and IL-2R expression may contribute to the immune inflammatory mechanism of alopecia areata.