The prevalence of seizure types among the subpopulation of patients referred for phase I neuropsychological assessment likely differs from the prevalence of specific seizure types within the general seizure population. Understanding the prevalence of clinical diagnoses is critical to maximizing the predictive value of any assessment or diagnostic technique, clinical neuropsychological assessment of patients with seizures being no exception. Data from a series of 835 patients referred for phase I neuropsychological evaluation are used to report the prevalence of specific seizure types, as well as neuropsychological and demographic characteristics. Considerations for clinical neuropsychological research and practice are briefly discussed. © 2006 Psychology Press.