Previous reports suggest that sex differences may exist in dreaming under anesthesia, but their results were inconclusive. The current study explored sex differences in the incidence and content of dreams during short propofol sedation for upper gastrointestinal endoscopy and investigated whether sex differences or dream content affect patient satisfaction with sedation. A total of 200 patients (100 men and 100 women) undergoing upper gastrointestinal endoscopy participated in this study. Patients were interviewed with the modified Brice questionnaire about the incidence and the content of dreams, and satisfaction with sedation was assessed. The results showed that the incidence of dreaming was significantly higher in men (31%) than in women (17%) (P=0.02), but recovery time was similar. In men, 45% (14/31) of dreamers reported positive emotional content and only 6% (2/31) reported negative emotional content. In contrast, in women, 18% (3/17) reported positive and 29% (5/17) reported negative content (P=0.04). Men reported dreams that were more vivid, meaningful, familiar, and memorable (P<0.01). No significant sex differences were observed in the emotional intensity of dreams, and emotional content did not influence patients' satisfaction. In sum, sex differences existed in dreaming during short propofol sedation despite similar recovery time and matching in terms of age. Men reported dreaming more frequently and had a higher incidence of recall for their dream narratives. In particular, men reported significantly more positive emotional content, less negative emotional content, and more meaningful content. Dreamer satisfaction with sedation was not influenced by sex or dream content.