The neutrophil to lymphocyte (N/L) ratio is a recently described independent predictor of death/myocardial infarction in patients who have undergone coronary angiography. We hypothesized that an elevated N/L ratio would be a predictor of long-term mortality in patients undergoing percutaneous coronary intervention (PCI). A total of 1,046 patients who underwent PCI were divided into tertiles based on their preprocedural N/L ratio (mean N/L ratio, tertile 1, 1.7 +/- 0.5; tertile 2: 3.2 +/- 0.6; tertile 3, 11.2 +/- 12.9). Vital status was assessed using the Social Security Death Index. There were a total of 144 deaths over a mean follow-up of 32 months. The best survival was seen in tertile 1, with an increase in long-term mortality seen in tertiles 2 and 3 (p <0.0001). In multivariable modeling, after adjusting for age, chronic obstructive pulmonary disease, left ventricular ejection fraction, serum hemoglobin, serum creatinine, and lesion severity, the log N/L, but not the white blood cell count, was an independent significant predictor of long-term mortality (hazard ratio 1.85, 95% confidence interval 1.3, to 3.04, p = 0.01). The risk persisted when patients with an acute myocardial infarction were excluded from the analysis (hazard ratio 2.46, 95% confidence interval 1.4 to 4.4, p = 0.002). In conclusion, an elevated preprocedural N/L ratio in patients undergoing PCI is associated with an increased risk of long-term mortality.