WisMon (see URL http://www-sop.inria.fr/planete/software/WisMon/ ) is a wireless statistical monitoring tool. It does sniffing on the medium using a multiple probe approach. The probes synchronize the timestamp of each received packet to the beacon timestamp. This method allows the system to build a single list of packets. The captured data is processed in realtime to obtain Received Signal Strength (RSSI), inbound and outbound traffic, packet retries and transmission mode vs. time. All these parameters can be obtained in a per-station basis. The WisMon tool fulfills a gap on the wireless experimental field: it provides physical parameters on realtime for evaluation during the experiment, records the data for further processing and builds a single view of the whole wireless communication channel environment. The client-server approach allows the user to distribute the capture, processing and display functions into different and remote stations, provided they comply with the required network bandwidth. WisMon collects the results and simplifies parameter extraction on WLANs. It is available as open source under the Cecill license. One of the first utilization of WisMon has been to experimentally evaluate different multicast transmission mechanisms for IEEE 802.11 WLANs, see 2 .