Despite widespread belief in the extinction burst as a common occurrence, relatively little empirical work has focused directly on the phenomenon. In order to provide additional data on the topic, we report reanalyses of published extinction-control groups from our laboratory following training with a variety of schedules and reinforcers. In addition, two prospective experiments were conducted in which rats responded for food on FR 5 or FR 1 schedules prior to a within-session transition to extinction. The results of these reanalyses and experiments suggest that the obtained prevalence of the extinction burst was considerably greater when response rates in the first minute of the transition to extinction were considered as compared to when session-wide response rates were considered. In addition, when reinforcement time was included in baseline response-rate calculations, the obtained prevalence of the extinction burst was higher than when reinforcement time was omitted. These findings highlight the importance of measurement and definitional issues in the obtained prevalence of the extinction burst. Further, a closer alignment of such issues across basic and applied research would be desirable in terms of the development of future theories describing the processes giving rise to the extinction burst.