The routing and signaling protocols for supporting multipoint-to-multipoint connections in ATM networks have been presented earlier. VP-merge and VC-merge techniques have been proposed as the likely candidates for resolving the sender identification problem associated with these connections. The additional buffer requirements in the VC-merge mechanism and the excessive rise of VPI/VCI space in the VP-merge mechanism have been the main reasons for concern about their effective utility. We propose improvements to the traditional VC-merge technique to minimize the need for additional buffers at intermediate merge points. Aptly named dynamic multiple VC-merge (DMVC), fixed multiple VC-merge (FMVC) and selective multiple VC-merge (SMVC), these mechanisms define a generic scheme for merging the data from multiple senders onto one or more outgoing links. By appropriately choosing the number of connection identifiers per connection, these schemes lead to a large reduction in the buffer requirements and an effective utilization of the VPI/VCI space. Based on extensive simulations, we show that by using two connection identifiers per connection, there is an 80% reduction in buffer requirements for DMVC and FMVC when compared to the buffer required for traditional VC-merge.