This study explores the intersubjective and dynamic construction of modal meanings in Chinese discourse. Specifically, it examines the role conversational repair plays in ascertaining the entailments of modal meanings such as obligation, possibility and permissibility, specifying the range of modal strengths, and assigning an emergent and negotiated quality to these meanings. It argues that repair shapes and sharpens speakers' modal stances, especially when the modal expression is polysemous. Illustrative data are drawn from 30 hours of audio/video recorded interaction in weekend Chinese language schools.