This article presents an empirical evaluation of Martin Ehala's (2007) mathematical model of ethnolinguistic vitality (EV). The model is here applied to assess the vitality of Taiwan's native Bensheng group (native Taiwanese speakers of Southern Min) by means of a comparison with the local Waisheng ethnolinguistic group (Mainland Chinese speakers of Mandarin). Traditionally, the EV-model measures the attitudes toward two distinct groups and their languages and cultures. In this article, we use the formula to deal with Taiwan's cultural complexity by including bilingual and hybrid identities into the EV-model. After an overview of the basic principles of the mathematical model and some essential facts about the Southern Min language, we test and discuss the results from 298 written questionnaires offered in Taipei and Kaohsiung. We then evaluate the workability of the EV instruments as well as the vitality of the Southern Min speakers and their language in Taiwan as indicated through EV results. The article concludes with suggestions for further elaboration of the model.