Background: SURMOUNT-4 was a Phase 3 clinical trial evaluating the safety and efficacy of tirzepatide in adults living with obesity or overweight. The method of delivery for tirzepatide was via a weekly, single-use injection pen device. The aim of this qualitative interview study was to better understand the ease-of-use of the pen device used to administer the study medication. Methods: Exit interviews were conducted with a random sample of US-based participants who had completed their Week 88 primary endpoint and Week 92 safety follow-up visits in SURMOUNT-4. A semi-structured discussion guide was used to understand the participant experience of the study, including use of the single-use pen device. Participants also completed an Injection Device Experience Questionnaire (ID-EQ) during their interview. As of May 30, 2023, interviews are on-going; n = 79 have been completed. The intended total sample size is n = 90 interviews. Results: Most participants reported that the single-use pen device was easy to use, and this was reflected in their responses to the IDEQ item "Overall, the device is easy to use": 91% responded "Strongly Agree", and 9% responded "Agree." Participants commented that the device was convenient due to being pre-filled and packaged as an allin-one device, that administration was simple and required minimal steps to inject each dose, that using the device took very little time, and that the needle was small and caused little to no pain. The requirement for the drug (and therefore the device) to be kept refridgerated was the key limitation mentioned. Conclusions: Qualitative exit interview methodology was utilized to understand participants' overall experience during SURMOUNT-4. Participants in the SURMOUNT-4 clinical trial found the single-use injection pen device to be easy to use and convenient.