This study examined the speculation that the Wisconsin Card Sorting Test (WCST) might be a relatively culture-free neuropsychological test. The relationship between level of acculturation and performance on the Spanish version of the WCST was investigated, using a sample of Mexican American adults (N=52). When the sample was divided into two groups based on level of acculturation as measured by the Acculturation Rating Scale for Mexican Americans—2nd Edition, within-group contrasts demonstrated that higher levels of acculturation significantly improved performance on the WCST. The performance of this sample was compared to select Spanish norms, finding no clinically significant differences. Contrasts with English norms for the WCST yielded significant differences on a majority of the WCST measures, demonstrating that the English norms are inappropriate for use with this population. This study concludes that the WCST is not a culture-free neuropsychological test.