Introduction: Bilingualism is the norm worldwide. Despite the fact that nearly one in five individuals (17.9%; U.S. Census Bureau, 2007) speaks another language other than English in the home, knowledge regarding the nature of bilingualism and school performance, particularly vocabulary skills in bilingual children, is still needed. Purpose: This study investigated vocabulary skills of bilingual, Spanish-English speaking students enrolled in 3rd, 4th, and 5th grades. Methods: Fifteen Spanish-English speaking students were administered English and Spanish receptive and expressive vocabulary measures. Total conceptual vocabulary scores were also obtained for both the English and Spanish measures. Results: Results indicated significant differences for 3rd and 5th grade groups on the Spanish expressive vocabulary measure and also on the expressive total conceptual vocabulary measure. Conclusions: The bilingual students, although the majority had been mainstreamed and exited from ESOL classes and services, appeared to be still acquiring English vocabulary skills and may have not attained complete cognitive academic English language proficiencies. Therefore, it is possible that incomplete vocabulary skills may affect overall academic language skills and overall academic performance. Speech-language pathologists (SLPs) must strive to maintain native language skills that facilitate reading comprehension and English academic success.