We investigated whether an active learning approach, facilitated by a personal response system, would lead to improved student engagement and learning outcomes in large-group physiology lectures for undergraduate science students. We focused on encouraging students' active learning in lectures, whereas previous studies have made more use of audience response technology during lectures for formative or summative assessment. Students voluntarily answered questions posed during lectures with their personal response system (clickers), with individual answers automatically collated for immediate histogram display. This feedback then dictated the focus of followup discussions in the lecture. Student and instructor attitudes were surveyed through voluntary interviews with student responses correlated with their degree of clicker participation and individual exam results. Active lectures were found to increase both student motivation and engagement. Students who participated in answering questions achieved better results than students who chose not to. Students with the lowest scores in a prerequisite course (previous semester physiology exam marks of less than 60%) showed significantly better outcomes from the use of clickers than both middle-achieving (60-75%) and high-achieving (greater than 75%) entry students. Significant improvement was evident in both mid- and end-semester exam results compared with student cohorts from preceding years, although this could also be influenced by many other factors. Increased student engagement and the immediate feedback obtained during lectures were advantages commonly noted by lecturing staff. (Contains 4 tables and 8 figures.)