This article describes five dialect-based changes in progress in the Southern Basque town of Oiartzun. Based on data collected in sociolinguistic interviews with thirteen local Basque speakers, this article examines dialectal variation in elements chosen from different parts of the grammar: two lexical items, two morphosyntactic alternations on auxiliary verbs, and a phonological process, apheresis. In particular, several claims are made about dialect contact in Oiartzun. Strong apparent-time evidence exists that four out of five of these elements are undergoing change. Older speakers tend toward forms characteristic of dialects to the east of Oiartzun, whereas younger speakers prefer western forms. In each case, male speakers appear to be leading the process of change; men show significantly higher frequencies of incoming western forms than women. The data, however, provide little support for the hypothesis that the recently introduced Basque literary standard has influenced young people's vernacular.I am deeply grateful to the people of Oiartzun for their generous support and hospitality during my stay in their beautiful town. Special thanks to Iñaki Arbelaitz for sharing with me his encyclopedic knowledge of local culture, language, and geography. Also, thanks to Larraitz Sanzberro, Katrin Abal, Inazio Retegi, Xabier Artiagoitia, Roslyn Frank, and Toki Alaiko denak. Thanks to John Singler for invaluable theoretical and methodological guidance in this study and to Renée Blake, Begoña Echeverria, Gregory Guy, John Singler, Koldo Zuazo, and two anonymous reviewers for helpful comments on earlier drafts. All shortcomings are my own.