The purpose of this study was that of attempting to clarify discrepant results regarding classificatory accuracy of the Russell, Neuringer and Goldstein (1970) Process Key. The Process Key is the component of the neuropsychological keys that classifies cases as having recently or remotely acquired brain damage on the basis of level of performance and severity of lateralizing signs. A correct classification of acute brain damage occurs when onset of illness began within 3 months of time of testing. A study of stroke patients indicated that time since onset is an inadequate criterion for producing a satisfactory classificatory level, but time of onset in combination with type of stroke was associated with a high degree of classificatory accuracy. In particular, patients with recent thrombotic/hemorrhagic type strokes were classified as acute with a very high accuracy level, but the classification was substantially less accurate for recent stroke patients with other tyoes of stroke, and for cases that were not of recent onset.