This study aimed at investigating the perceptions of using first language (Arabic) in the ESP classroom from the viewpoints of both students and teachers of the Preparatory Year Department at an applied medical college in Saudi Arabia. It also intended to find out if there were significant differences in perceptions according to variables like gender and college level. Surveying 92 students and 10 teachers through a questionnaire and interviews, the results revealed that instructors’ and students' viewpoints of L1 use in their medicalEnglish classes were considerably negative. No statistical differences in the students' perceptions were noted according to college level; however, there were slight differences due to gender variable; females were more to disagree with more L1 use in the classroom. Despite their negative views, instructors stated differences between students due to both gender and college level, believing that males and Level 1 students need more L1 while teaching medical English than females and Level 2 students.