The reliability and validity characteristics of the Western Aphasia Battery (WAB) are described. High internal consistency measures and high test-retest reliability argue for stability of the test both because its parts contribute to the composite index and because of its temporal reliability. Inter- and intrajudge reliability are both very high, suggesting consistent scoring within and between scorers. The WAB satisfies face- and content-validity criteria. Results from the WAB and the Neurosensory Center Comprehensive Examination for Aphasia (NCCEA) highly correlate, indicating good construct validity. WAB AQ scores and Raven's Coloured Progressive Matrices scores significantly correlate, suggesting that the language portions of the WAB are not totally independent from nonverbal functioning. WAB AQ scores reliably differentiate between aphasic and control groups, with only a small overlap for high functioning anomic aphasic subjects.