The current study describes the development and validation of a novel scale (BILEX) designed to assess young bilingual children's receptive vocabulary in both languages, their conceptual vocabulary, and translational equivalents. BILEX was developed to facilitate the assessment of vocabulary size for both of the children's languages within one session without any transfer from one language to the other. One-hundred-and-eighty-two 3-year-old children participated in the studies of reliability and validity. Psychometric properties have very good consistency and reliability, along with good concurrent, construct, and criteria validity.