The performance of 11 Alzheimer's (DAT) and 8 anomic aphasic stroke patients is contrasted with that of 32 normal elderly subjects on both the Boston Naming Test (BNT) and the Controlled Oral Word Association Test (COW), a letter-category verbal-fluency test. While both tests require phonological processing, only the BNT requires semantic processing (object recognition). Both DAT and anomic aphasic stroke patients were significantly impaired on the BNT, with mean z scores (based on the performance of the normals) of -4.08 and -2.57, respectively; the DAT patients were significantly farther from normal than were the anomic aphasics. Their relative levels of impairment on the COW were reversed: The anomic aphasics' performance (z = 1.79) was worse than that of the DATs (z = -0.66). This pattern of performance on the two tests is consistent with the hypothesis that impaired word finding reflects impaired processing mainly of semantic information for the DAT subjects, mainly of lexical-phonological information for the anomic aphasic subjects.