Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. The IEEE 802.11 wireless LANs standards specify how to send multicast frames with no ACK and using one of the Basic Service Set (BSS) rates. This situation has led many researchers to design techniques aiming to improve reliability of a multicasting mechanism. The Leader-Base Protocol (LBP) is one such mechanism proposed in the literature that is the most promising approach. The main idea behind the design of the LBP mechanism is to reduce the probability of collision of the feedback messages sent by the multicast group members. However, the LBP mechanism falls short by not considering the varying conditions characterizing the wireless channels. In this paper, we introduce a novel auto rate selection multicast mechanism for multi-rate wireless LANs, namely ARSM (Auto Rate Selection for Multicast), capable of adapting the data transmission to the varying conditions of the channel. Our simulation results show that our new scheme outperforms the IEEE 802.11 and the LBP mechanisms. © IFIP International Federation for Information Processing 2006.