This study compared the use of selected epistemic modals in English speech of Chicano barrio residents and Anglo visitors to the community. Transcribed conversations served as the database. The Chicano speakers tended to use the epistemic modals only to index the evidential weight of propositions, whereas the Anglo speakers tended also to use them for numerous non-evidential functions, most frequently for negative politeness. In this paper, I discuss those epistemic modal functions used the most disparately between the two groups. These differences in epistemic modal use are shown to relate to cross-culturally different uses of epistemic modality for politeness. Sociocultural explanations for this disparity are proposed: the different patterns of epistemic modal use which emerge are argued to be tied to different, culturally based epistemologies held by the two groups