It has been suggested by Kurt Goldstein, MD, that conduction aphasia is a disturbance of “inner speech.” We tested this hypothesis in five patients who had conduction aphasia with similar speech disturbances. The patients were presented with pictures and were required to perform, without overt vocalization, comparisons of word length and homophonic and rhyming matches. Four patients successfully performed such judgments on words they could not vocalize, but one patient could not. These findings suggest that the hypothesis may have been correct for only a subgroup of conduction aphasics. The findings also provide evidence for heterogeneity within the class of conduction aphasia. © 1986, American Medical Association. All rights reserved.