Objective: Self-reported screening questions are considered as an effective way to identify patients with limited health literacy. Yet research has shown that individuals tend to over-report their reading level. Moreover, the likelihood of over-reporting may differ between gender groups. This study examined if systematic differences exist between men and women in their response to self-reported screening questions. Design: A national survey in Taiwan with participants selected using a multistage stratified, probability-proportional- to-size sampling strategy. Participants: A total of 5682 Taiwanese adults aged 18 and older were sampled and recruited. Of those adults, 3491 participated in the survey, resulting in a 62.1% response rate. Both gender groups were equally represented in the final study sample. Main measures: Self-reported health literacy was assessed using two sets of questions that asked how difficult it was for the respondent to understand written health materials and how often the participant needed assistance from others to understand written health materials. The objective level of health literacy was measured using the Mandarin Health Literacy Scale (MHLS). Results: A significant gender difference was observed among participants who had inadequate health literacy: while women's self-report was in line with the MHLS test result, men had a significant tendency to over-report their comprehension of health information. Conclusions: In Taiwan, screening questions are prone to socially desirable response and may underidentify male patients with inadequate health literacy. Development of a brief and easy-to-use health literacy test may be a more effective approach to health literacy screening in clinical settings. Alternatively, clinicians can verify patient comprehension of health information via the 'teach back' or 'show me' technique in order to improve communication and patient care. Research is needed to examine if gender differences in self-report of health literacy exist in other countries.