ZigBee is a communication standard which is considered to be suitable for low-rate and low-power wireless sensor networks.When forming a ZigBee network, a device is said to join a network successfully if it can obtain a network address from a parent device. The parent device can locally decide addresses for its child devices by the ZigBee address assignment scheme. The assignment scheme is easy to implement, but the network address utilization may be low. In another words, some devices can not join the network. This chapter describes the ZigBee network formation problem and introduces a solution.