The purpose of this study was to assess the dimensionality of two forms of a large-scale standardized test separately for 3 ethnic groups of examinees and to investigate whether differences in their latent trait composites have any impact on unidimensional item response theory true-score equating functions. Specifically, separate equating functions for African American and Hispanic examinees were compared to those of a Caucasian group as well as the total test taker population. On both forms, a 2-dimensional model adequately accounted for the item responses of Caucasian and African American examinees, whereas a more complex model was required for the Hispanic subgroup. The differences between equating functions for the 3 ethnic groups and the total test taker population were small and tended to be located at the low end of the score scale.