Blended synchronous learning involves using rich-media technologies to enable remote and face-to-face students to jointly participate in the same live classes. This article presents blended synchronous learning designs from seven case studies that were part of a project funded by the Australian Government Office for Learning and Teaching and articulates principles for implementation as espoused by the teachers who enacted them. A wide range of technologies (including video conferencing, web conferencing and virtual worlds), tasks (namely collaborative evaluation, group questioning, class discussion, problem solving and collaborative design) and levels of student interaction (from lightweight to tightly coupled) were present within the designs. The main issues that teachers confronted when facilitating blended synchronous lessons were those relating to communication and those relating to cognitive overload caused by split attention. Key pedagogical principles for enactment as identified by the lead teachers included the need for extensive preparation, clear instructions, composure, flexibility, advance preparation of students and savvy utilisation of support staff.