Moderate nonfluent aphasia following a left parietotemporal lesion was found in the native language of one bilingual patient, in contrast to less severe, fluent aphasia in the patient's secondary language. Conversely, mild anomia was found in the native language of a second patient, while global aphasia was found in the secondary language. His lesion was located in the left posterior frontal area. These examples of differential aphasia were assessed by standard aphasia tests and by language inventory translated into the appropriate languages. We propose that differential aphasia resulting from a single hemispheric lesion is related to the disruption of different basic cognitive functions, which participate to varying degrees in the performance of the languages affected. In terms of neurolinguistic theory, the findings in these patients support the observation that most frequently used language is the first to recover. They refute the notion that the native language recovers first.