This paper focuses on a 3-year, longitudinal study of the implementation of coteaching, as an innovative approach for preparing high school science teachers enrolled in an undergraduate science teacher education programme located in the United States. The coteaching/co-generative dialogue/co-respect/co-responsibility dialectic is introduced as a way to conceptualise coteaching practice and support successful implementation. We also discuss means to introduce coteaching into the preservice programs and report on findings from an evaluative study of the implementation process. Coteaching has the potential to re-conceptualise teacher preparation and professional development models for science teachers.