In the paper, we consider a preference heterogeneity problem in large-scale multicast applications. Abundant content, data type and diverse members' interests naturally lead to preference heterogeneity within a multicast session requiring frequent communication within subgroups of members sharing common interests/requirements. In this paper, we take an overlay approach which builds topology-sensitive subgroup communication (TSC) structures to support efficient subgroup communications in large-scale multicast applications. Our TSC mechanism completely eliminates additional creation of multicast groups while minimizing the exposure of unnecessary packets to members and links. Our mechanism exploits the spatial locality of members within a given subgroup, and enables members to autonomously build a TSC structure consisting of multiple unicast and scoped multicast connections. Simulations using real topology data show that TSC mechanism performs well for diverse configurations with d...