Purpose: Vocabulary assessment holds promise as a way to identify young bilingual children at risk for language delay. This study compares 2 measures of vocabulary in a group of young Spanish-English bilingual children to a single-language measure used with monolingual children. Method: Total vocabulary and conceptual vocabulary were used to measure mean vocabulary size and growth in 47 Spanish-English bilingually developing children from 22 to 30 months of age based on results from the MacArthur-Bates Communicative Development Inventory (CDI; Fenson et al., 1993) and the Inventario del Desarrollo de Habilidades Comunicativas (Jackson-Maldonado et al., 2003). Bilingual children's scores of total vocabulary and conceptual vocabulary were compared with CDI scores for a control group of 56 monolingual children. Results: The total vocabulary measure resulted in mean vocabulary scores and average rate of growth similar to monolingual growth, whereas conceptual vocabulary scores were significantly smaller and grew at a slower rate than total vocabulary scores. Total vocabulary identified the same proportion of bilingual children below the 25th percentile on monolingual norms as the CDI did for monolingual children. Conclusion: These results support the use of total vocabulary as a means of assessing early language development in young bilingual Spanish--English speaking children.