The present paper argues that discussion of the role of reasoning in clinical neuropsychology has been largely restricted to a debate over the reliability and validity of end-stage decision-making. This has sometimes led to heated debate, but has not resulted in any careful consideration of either the process of clinical reasoning or the cognition of the clinician. There is already a wealth of theory and research on the kinds of errors typical of human judgement and decision-making. Moreover, much of this work is particularly relevant for neuropsychology, being frequently based on research on medical diagnosis. This literature is briefly reviewed, with examples that demonstrate the relevance of research in this area for clinical neuropsychology. Then, a step-by-step approach is taken to examining the process of clinical neuropsychological assessment, with consideration at each step of some of the issues that arise demanding clinical reasoning. Finally, the article is briefly summarised and some implications for clinical training are advanced.