A preemptive roaming mechanism in wireless network environments. In one implementation, the present invention provides a wireless client that implements a preemptive roaming mode that, when an attribute of the signal (e.g., Signal to Noise Ratio (SNR), etc.) between the access point with which the client is currently associated crosses a threshold, scans for other access points with which to associate. In one implementation, the client switches between the scanning mode and a traffic mode to allow data to be transferred between the client and the current access point. The pre-emptive roaming functionality can be configured to support desired data rates or other QoS levels.