Components of the adaptive immune system, in particular lymphocytes and immunoglobulin, play a major role in advanced atherosclerotic lesions. We sought to determine whether routine, measurements of the relative number of circulating lymphocytes (%L) and gamma-globulin (%G) reflecting immunoglobulin are related to event-free survival in patients with stable coronary artery disease (CAD). We prospectively studied the combined endpoint all-cause mortality, myocardial infarction and coronary revascularization procedures in 141 patients after successful percutaneous coronary intervention during a median follow-up time of 13.2 years. Using Cox regression, we found a significant influence of %L on event-free survival (P=0.007) with a relative risk of 2.21 comparing third to first tertile. Subjects with higher %G values likewise had a shorter event-free survival (P=0.008) with a relative risk of 1.67 comparing third to first tertile. The predictive value of %L and %G remained significant after adjustment for demographic data, cardiovascular risk factors, extent of CAD and other inflammatory markers. We conclude that the fraction of gamma-globulin and in particular the relative lymphocyte cell count may serve as readily available and reliable prognostic tools for the long-term outcome in patients with stable CAD.