Abstract: The invention is directed to techniques for synchronizing the internal clocks of two devices, such as an implantable medical device and an external device, with reduced reliance on periodic polling. In one embodiment, the invention is directed to a technique in which one of the devices computes a time drift. The time drift may occur because the internal clock of one device may run more slowly than the internal clock of the other device. One device may poll the other as a function of the time drift. In another embodiment, a system of medical devices synchronizes internal clocks to a time signal generated by a time reference.