Background: There are no studies in the literature related to the effect of beta blockers (BB) on changes in C-reactive protein (CRP) levels after percutaneous coronary intervention (PCI). Hypothesis: We designed a prospective randomized study to investigate the impact of BB therapy on CRP in patients who underwent elective PCI. Methods: In all, 300 patients with coronary artery disease were included. Patients were randomized to either a metoprolol or to a control group before PCI. Blood samples for CRP levels were obtained before BB treatment, and at the 6th, 24th, and 36th h after PCI. Results: Of 300 patients, 150 received metoprolol 100 mg/day (mean age, 59.0 +/- 10.2 years; 106 men, 44 women), and 150 received no BB (mean age, 59.8 +/- 9.8 years; 114 men, 36 women) and served as the control group. Baseline clinical characteristics of both groups were similar. Basal CRP levels between the two groups were similar. Of the patients included in the study, 40.8% in the BB group and 39.6% in the control group had elevated basal CRP levels. The CRP levels increased above baseline values in 85% of patients in the BB group and in 89.3% of patients in the control group (p > 0.05) during follow-up. The CRP levels in patients in the BB group at the 6th, 24th, and 36th h were lower than those in the control group; however, this difference did not reach statistical significance. Conclusions: Prior BB therapy seems to have no effect on CRP levels after PCI.