The present study was designed to assess the role of response time on the Category Test of the Halstead-Reitan Neuropsychological Test Battery (HRNB). The intent was to define the underlying constructs of the Category Test more particularly, the speed of performance by examining response time to individual slides of the Category Test.Seventy-two normal adult volunteers were administered the complete HRNB. Average response times were computed for correct (CRT), incorrect (IRT), and total (TRT) scores on the Category Test. The efficacy of using response measures (CRT, IRT, and TRT) to predict Category performance was examined in the context of other HRNB variables that loaded factorially with the Category Test, more specifically: TPT-time, memory, and location, Trails B, WAIS-R Block Design, and WAIS-R Object Assembly.A step-wise multiple regression analysis was computed using the above HRNB and response time measures to predict Category error scores. Results from this analysis indicated that TPT-location, TRT, and IRT contributed significantly (p<.05) in the prediction of Category scores. Approximately 15% of the variability in Category scores was explained by a measure of spatial memory (TPT-location) and an additional 15% was accounted for by psycho-motor speed (TRT and IRT). The significant contribution of response time in defining the underlying construct of the Category Test was discussed in terms of possible implications for enhancing the neuropsychological significance of the Category Test.