Abstract: In bilingualism research, language dominance has been conceptualized and operationalized in different ways. In this paper, we discuss this notion and investigate to what extent language dominance is congruent with vocabulary knowledge in each language. First, we summarize definitions and operationalizations of language dominance. We show that comparison of proficiency related measures is a common operationalization of language dominance. Yet, the importance of attitudinal, biographical, or use-related components is often stressed. Such components are included in survey instruments like the Bilingual Language Profile (BLP). Second, we analyze data on language profiles of 225 French/German and 70 Italian/German adult bilinguals. Correlation and regression models are fitted to investigate the relation between the multi-dimensional dominance metric (BLP) results and results based on lexical tests (LexTALE for German and French, the VSPT from Dialang for Italian). The results reveal a strong linear association between BLP and LexTale.