Race and ethnicity are commonly used predictor variables in medical and public health research. Including these variables has helped researchers to describe the etiology of certain disease states. Including race and ethnicity in research has been hypothesis generating in terms of the relationship between genetic and environmental factors in the development of disease. Eliminating health disparities among different racial and ethnic groups has become a national priority. However, incorporating race and ethnicity into health research is complex because these variables are difficult to define and individuals often identify with more than one race or ethnicity. As a "minority-majority", multiethnic, multiracial state, Hawai'i faces unique challenges in incorporating race and ethnicity into research. As the demographics of the United States continue to evolve, many of the challenges faced in Hawai'i will apply to the United States as a whole.