Clinicians are frequently faced with the task of differentiating between pulmonary tuberculosis (PTB) and pneumonia. We evaluated the role of the C-reactive protein test (CRP) for differentiating between TB and pneumonia among military personnel in South Korea. Only immunocompetent males were eligible. Forty-six patients with PTB and 67 with pneumonia were enrolled prospectively. Median CRP concentration was lower in patients with TB than in patients with non-tuberculous pneumonia (3.2 mg/dl [range 0.1-15.7 mg/dl] vs. 8.3 mg/dl [range 0.2-33.7 mg/dl], P < 0.001). The sensitivity and specificity for TB of a low CRP concentration (< 11.2 mg/dl) in serum was 93.3% and 40.9%, respectively. CRP concentration measurement might be useful for eliminating the diagnosis of TB.