Introduction: Sedative-hypnotics overdose, one of suicide method is commonly observed in drug overdose patients in the emergency department. The purpose of this study was to investigate the risk factors of aspiration pneumonia in patients with sedative-hypnotics overdose. Material & Methods: Sedative-hypnotics overdose patients who visited our ED between 2009 and 2015 were included. This study was conducted retrospectively, with collection of data by review of medical records. We included the patients who had only sedative-hypnotics. 178 patients was finally included in our study. We investigated the characteristics of the patients and classified them according to two group based on the presence of aspiration pneumonia. Logistic regression analysis was performed to investigate the factors associated with the development of aspiration pneumonia. Results: In this retrospective analysis, age, amount of drug ingestion, GCS score at admission (Glasgow Coma Scale), history of hypertension and diabetes mellitus, hypotension at admission were significantly different between two groups. Age, amount of ingestion and GCS score at admission were associated with aspiration pneumonia in the multivariate logistic regression analysis. Conclusion: The risk of aspiration pneumonia in the patients of sedative-hypnotics overdose is associated with old age, amount of drug ingestion, GCS score at admission.