The instruction of mathematically talented students (MTS) in heterogeneous classes is an issue of debate. Questions of equity, differential instruction, teacher awareness of their talented students' needs, and their willingness and competence to face the challenges of nurturing these students are all raised within this context. Our international study compared South Korean, American, and Israeli teachers of mathematics perspectives concerning their (a) perceived competence to teach MTS (b) perceived competence in addressing MTS' needs through differential instruction, (c) support for separation of MTS into special math classes, and (d) equity views concerning MTS' needs. Data was collected by means of a questionnaire presented to 80 South Korean, 145 Israeli, and 58 American teachers of mathematics. Findings suggested that most teachers in these countries perceived themselves as competent to teach MTS, while very few of the participants supported the separation of MTS into special classes. South Korean teachers perceived themselves to be less competent in teaching MTS as well as in applying differential instruction and agreed more than their foreign counterparts that the fostering of mathematically weak students is more important than the fostering of MTS. Teachers who had some mathematical background appeared to perceive themselves as more competent to teach MTS than teachers who had no mathematical background. Teachers who predominantly taught large classes felt less competent to teach MTS than teachers who predominantly taught medium-sized classes. Findings were partially interpreted within the perspective of cultural differences. Recommendations for teachers' professional development are drawn.