Objective: to determine the incidence of linezolid-induced haematological toxicity and study the influence of renal clearance on its appearance and the preventive effect of pyridoxine. Methods: a retrospective observational study was conducted. Every patient treated with linezolid in a university hospital during 6 months was included. Haematological toxicity was defined as a decrease of 25% in hemoglobin, of 25% in platelets and/or 50% in neutrophils from baseline. The incidence of haematological toxicity and the percentage decrease in analytical variables were compared in patients with and without renal failure (creatinine clearance lower than 50 mL/min), using the 30 mL/min threshold, and with or without pyridoxine; using Chi -Square and U Mann-Whitney tests, respectively. Results: thirty-eight patients were evaluated. Sixteen (42%) presented haematological toxicity (2 due to a decrease in haemoglobin, 9 in platelets and 8 in neutrophils). Two patients (5%) discontinued treatment due to thrombocytopenia. Toxicity incidence was similar in patients with and without renal failure, 42% vs 42%, p = 0.970, with more or less than 30 ml/min, 67% vs 40%, p = 0.369, or with or without pyridoxine, 47.8% vs 33%, p = 0.376. Patients with renal failure had a significantly greater reduction in platelet count, p = 0.0185. Conclusion: forty-two percent of patients had haematological toxicity, being more frequent platelets and neutrophils reduction. This was not significantly higher in patients with renal failure or in those without pyridoxine. Greater reduction in platelet count was observed in patients with renal failure.