We investigated the relation between the activation of T lymphocytes and the occurrence of restenosis after percutaneous transluminal coronary angioplasty (PTCA) in 10 stable angina patients. Recent studies have suggested that PTCA causes an inflammatory response, which may affect restenosis after angioplasty. Soluble interleukin-2 receptor (sIL-2R) is a useful marker to evaluate the activation of T lymphocytes. sIL-2R was measured before and 2 h after successful PTCA, and 3-month follow-up coronary angiography was done to observe restenosis. Four of 10 patients showed restenosis. The restenosis group of 4 patients had a higher level of sIL-2R after PTCA than the no-restenosis group of 6 patients (495 vs. 274 U/ml, p < 0.01). This study suggests that sIL-2R may offer prognostic information after elective PTCA and identify a subgroup of patients at high risk for clinical restenosis in a few months.