In this longitudinal recovery study of severe aphasia, subjects were tested five times at 6-month intervals with the Boston Assessment of Severe Aphasia (BASA), for a period of 2 years post onset. The majority of subjects had global aphasia (n = 17), but five had severe Wernicke's aphasia, and two had other varieties of severe aphasia. Significant improvements in communicative functions were noted for up to 18 months post onset, but the greatest improvement occurred in the first 6 months post onset. Most subjects did not change aphasia classification during the 2-year period. Initial individual BASA cluster (subtest) scores were less accurate than the 6-month scores in the prediction of later BASA Total scores. Cluster scores obtained at 6 months post onset could reliably predict BASA Total scores at 24 months post onset.