This study investigates the utility and validity of the MacArthur–Bates Communicative Development Inventory (CDI) for use with low-income parents and their 24- to 36-month-old Spanish–English bilingual children (n = 79). Issues in the interpretation of the integrated CDI/Inventarios del Desarrollo de Habilidades Comunicativas (IDHC) score to index bilingual children's overall conceptual knowledge are also considered. Results indicate that the CDI/IDHC can be used with this population through at least age 36 months and parents are accurate reporters of their children's Spanish and English vocabulary. The value of the integrated score was confirmed. However, given the lack of norms associated with the integrated score, the complexity of determining how best to interpret this score was underscored.