Objective To evaluate the characteristics of dysphagia after brain stem infarction, and to determine the mechanism of aspiration. Methods The fluoroscopic videos of 12 dysphagia patients who had suffered brain stem infarction and 10 healthy counterparts were analyzed quantitatively using a digital analysis system. Each participant was requested to twice swallow 5ml of thick liquid. The observations included the oral transit time (OTT), the swallow response time (SRT), the hyoid movement time (HMT), the upper esophageal sphincter opening time (UOT) and the laryngeal closure time (LCT). An 8-point penetration-aspiration scale (PAS) was used to evaluate the severity of aspiration, and the results were correlated with the other 5 quantitative observations. Results The average OTT [(3.091±1.803)s], HMT [(1.498±0.550)s] and LCT [(0.651±0.186)s] of the brain stem infarction patients were all significantly longer than those of the healthy controls. However, no significant differences were found between the patients and the healthy volunteers in terms of SRT or UOT. Aspiration severity was significantly correlated with SRT but not with LCT. Conclusion Dysphagia after brain stem infarction involves both the oral and pharyngeal phases. OTT, HMT and LCT can be used to quantify dysphagia after brain stem infarction, while SRT is a predictor of aspiration. Key words: Brain stem infarction; Dysphagia; Videofluoroscopy