Rationale : The cognitive science literature suggests both advantages and disadvantages of bilingualism for cognitive performance. However, little is known about the generalizability of such findings to clinical neuropsychology for diagnosing brain dysfunction in Spanish dominant bilinguals in the U.S. The present study examined the effects of bilingualism on Spanish-language neuropsychological test performance, and whether or not these bilingual advantages could be explained by socioeconomic status (SES). Design : Forty seven Spanish monolinguals and 42 Spanish-English bilinguals from the U.S. - Mexico border region were selected based on a ratio of English words to total words produced on a verbal fluency task in both language. Effects of bilingualism on neuropsychological test performance were examined as means comparisons between groups with comparable education, age, and sex. SES contributions were examined by comparing the performance of 28 bilingual and 28 monolingual participants with comparable demographic characteristics, and self-reported SES on tests where bilingual advantages were previously found. Results : Controlling for education, bilinguals out-performed monolinguals on a test of executive function, and some tests of attention/working memory, and processing speed, with an unexpected advantage on a test of visual memory. No differences were found on tests of language abilities, learning, visuospatial, or motor skills. Bilinguals had higher childhood SES than monolinguals. After equating groups on childhood SES, bilinguals still outperformed monolinguals on tests of executive functioning (Trail Making Test B and Stroop Color-Word Interference Condition), a measure of attention and concentration (WAIS-R Digit Span), and a measure of processing speed (WAIS-III-Symbol Search). Conclusion : These findings suggest that bilingual advantages observed in the cognitive science literature are seen on some neuropsychological tests that are commonly used in clinical settings, suggesting that learning a second language improves performance in a person's native language. These results suggest that bilingualism likely confers a true neuropsychological advantage beyond what can be explained by SES and education differences. This needs to be considered when interpreting test performance, adding complexity to the generation and application of test norms in bilingual groups.