Acculturation is important to examine variables that differentiate members of ethnic groups so that interventions can be appropriately targeted. By using a population-based sample of Mexican-origin adults, we sought to validate an acculturation scale for Mexican-American populations. The acculturation instrument included eight items adapted from the Acculturation Rating Scale for Mexican Americans (ARSMA). By using principal component analysis, we calculated eigenvalues for the eight items. The first principal component accounted for 66% of the variance. Language spoken most of the time, by itself, explained 62.4% of the variance of the full model, whereas birthplace, by itself, accounted for 74%. Slight increases in correlation values were observed beyond a four-item model that included language spoken most of the time, language thought, ethnic identity, and birthplace. Future studies should compare this scale with other multidimensional scales.