It is well established that there are declines in basic cognitive functions associated with aging. However, for individuals with extensive knowledge in a particular domain (e.g. experts), there does not appear to be age-related limitations in performance. Although expert performance relies on certain fundamental cognitive processes, such as information processing and memory capacity, the strategy with which an expert maintains a high level of functioning in his/her domain may be altered. One may view this alteration as a sign of compensation for age-related limitation, or one may deem that this alteration of strategies is due to the natural course of extensive practice in the field. The aim of this paper is to explore diagnostic reasoning processes in an aging medical specialist. Specifically, this study explores what aspects of performance approximates that of a younger expert, and what aspects deviate from the current model of expertise in medicine.