【Abstract】Objective To determine the effects of linezolid on the routine blood indices and investigate the safety in the very old male patients with meticillin-resistant Staphylococcus aureus (MRSA) infection. Methods A total of 46 male patients (aged 83-95 years) with confirmed MRSA infection in Chinese PLA General Hospital from April 2012 to March 2013 were enrolled in this study. They were all treated with intravenous injection of 0.6g linezolid, once every 12h, for 10 to 14d. Their routine blood indices such as red blood cell (RBC), hemoglobin (HB), white blood cell (WBC), platelet (PLT) and reticulocyte (Ret) were compared before and after the treatment. The hemorrhage events were recorded during the treatment. Results After treatment with linezolid, the level of HB [(95.609±14.210) vs (102.478±15.941)g/L], count of WBC[×1012/L, (6.944±2.590) vs (8.728±2.277)], Ret [(1.124%±0.844%) vs (1.789%±0.831%)] and PLT[×109/L, (142.913±62.065) vs (227.304±56.250)] were significantly decreased compared with before treatment (P<0.01). Bleeding events occurred in 22 patients. Among them, 10 patients (22%) had 2 bleeding sites, 4 patients (9%) had 3 bleeding sites, 2 patients had ≥4 bleeding sites. Conclusion Linezolid decreases the serum levels of PLT, HB and Ret in very old male patients with MRSA. So a special attention should be paid to bleeding during the treatment.