In this pilot study, qualitative methodology was used to examine the clinical reasoning of four experienced occupational therapists as they presented and modified therapeutic activities to treat patients with spinal cord injuries. The therapists demonstrated the multi-layered thinking discovered in previous research, but hierarchical structuring of knowledge emerged as an unexpectedly dominant theme in their reasoning. Examples of hierarchical thinking about therapeutic activity included creating mental files of therapy tasks and materials sequenced from elementary to advanced and determining the level of difficulty at which to present an activity in order to build the patient’s skills in a stepwise manner The therapists reported that they learned to make decisions about the use of activities in treatment by observing skilled clinicians and by treating patients.