Objective: This study examined cardiac patients' knowledge and use of sublingual glyceryl trinitrate. Design: A non-experimental, retrospective descriptive design with a convenience sampling strategy was used. Setting and Subjects Participants were cardiac in-patients who were prescribed sublingual glyceryl trinitrate (SLGTN) at the study hospital. Main outcome measure(s): Participants' knowledge and use of SLGTN was assessed using the Sublingual Nitroglycerin Interview Schedule (SNIS) which is a valid and reliable tool. Results: Fifty-two in-patients from a general cardiac ward or coronary care unit were approached. A total of 41 (87.2%) participants were enrolled and all completed the survey. Participants' mean Knowledge score regarding SLGTN was 3.98 (SD=1.21), and the mean Use score was 3.68 (SD=1.12). Approximately one quarter of participants (24.4%) knew using SLGTN to prevent chest pain was an appropriate use for the drug. Males were significantly more likely to incorrectly transport their SLGTN than the females in the study (t=-5.316, df = 21.8, p=<0.000). Conclusions: Findings indicate that patients' have limited knowledge of and do not always appropriately use SLGTN, particularly in terms of the way men transport the medication. Therefore there is a need to develop and implement educational strategies to facilitate greater self-management of angina.