The Category Test, a major part of the Halstead-Reitan Neuropsychological Battery, was first described in a 1943 article by Halstead and Settlage. This paper reviews the development of the test, the psychometric properties of the instrument, available administration and scoring methods, discusses various interpretative strategies, and the empirical support for the test's clinical validity. Recent developments are then reviewed, as well as what the authors see as the future potential for this instrument.