Techniques for dynamically switching between synchronous and asynchronous operation modes in body area networks (BANs). One embodiment includes a method (400) for transitioning from an asynchronous mode to a synchronous mode in a medium access control (MAC) of a BAN. A device receiving a switch mode command (S410) performs the acts comprising: setting a timer to a time period specified in the switch mode command (S430); propagating the received switch mode command to other devices in the BAN (S440); upon expiration of the time period, tuning to a channel selected from a set of channels reserved for the synchronous mode (S460); and initializing a device to operate as either a master device or a slave device in the synchronous mode of operation (S470). Another embodiment includes a method (300) for transitioning from a synchronous mode to an asynchronous mode in a MAC of a body area networks (BAN).