This study describes first and second year university physics students' understanding and reasoning of the concepts, angular speed and angular acceleration. The analysis was based on student responses to various tasks presented to them during one hour long interviews. These responses were characterized from a phenomeno graphic research perspective developed by Marton (1981) and his colleagues at Gothenburg University in Sweden. The findings of the study are described by categories of description and by categories of reasoning. Categories of description characterize; students' conceptualizations of angular speed from different frames of reference, and the ways in which students make comparisons of the angular speeds of two objects. Categories of reasoning characterize the ways in which students were thought to reason about the concepts of angular speed and angular acceleration in several task settings. Interpretation of these findings are discussed with reference to the role a typical introductory physics textbook may have had in shaping the way in which students think about these angular kinematic concepts. Finally, instructional implications and directions for future research are given.