In the present study, the authors empirically investigated a multidimensional conceptualization of acculturation using the Bicultural Involvement Questionnaire-Short Version (BIQ-S; J. Szapocznik, W. M. Kurtines, & T. Fernandez, 1980). Baseline data from four prevention trials, representing a total of 893 adolescent and 880 guardian participants of Hispanic descent, were used to examine the factor structure of BIQ-S scores. Results of exploratory and confirmatory factor analyses supported a four-factor solution. The factors were labeled as follows: (a) Comfort With Use of Spanish Language, (b) Comfort With Use of English Language, (c) Enjoyment of Hispanic Cultural Activities, and (d) Enjoyment of American Cultural Activities. The findings support an expansion of the theoretical conceptualization of biculturalism and suggest that within both the heritage and the receiving cultures, comfort with language and enjoyment of other cultural components represent different factors. Measurement invariance analyses revealed stability of the factor structure, as well as some measurement differences, between adolescents and their guardians. (Contains 5 tables and 1 figure.)