Studies of the effect of therapy on the course of recovery from aphasia yield inconsistent results and permit no generalization to the population of aphasic patients. Future investigations of the efficacy of therapy should specify the nature of the language disorders treated, the limits of the period of spontaneous recovery, objective measurement of relevant behavioral changes, and the nature, intensity, and quality of therapy provided. In subject selection, age, educational and social status, intelligence, health, social milieu, etiology, site and extent of lesion, time lapse since onset, type of aphasia, and nonlanguage behavior characteristics should be controlled if interpretable results are to be obtained.