The totem-pole bridgeless power factor correction (PFC) rectifier has recently been recognized as a promising front-end candidate for applications like servers and telecommunication power supplies. This paper begins with a discussion of the advantages of using emerging high-voltage gallium-nitride (GaN) devices in totem-pole PFC rectifiers rather than traditional PFC rectifiers. The critical-mode operation is used in the totem-pole PFC rectifier in order to achieve both high frequency and high efficiency. Then, several high-frequency issues and detailed design considerations are introduced, including extending zero-voltage-switching operation for the entire line-cycle, a variable on-time strategy for zero-crossing distortion suppression, and interleaving control for ripple current cancellation. The volume reduction of differential-mode electromagnetic interference filters is also presented, which benefits greatly from MHz high-frequency operation and multiphase interleaving. Finally, a dual-phase interleaved GaN-based MHz totem-pole PFC rectifier is demonstrated with 99% peak efficiency and 220 W/in power density.