Characterizing the properties of peer-to-peer (P2P) overlay topologies in file-sharing applications is essential for understanding their impact on the network, identifying their performance bottlenecks in practice, and evaluating their performance via simulation. Such characterization requires accurate snapshots of the overlay topology which is difficult to capture due to the large size and dynamic nature. Previous studies characterizing overlay topologies not only are outdated but also rely on partial or potentially distorted s. In this extended abstract, we briefly present the first characterization of two-tier Gnutella topologies based on recent and accurate snapshots. Categories and Subject Descriptors C.2.4 [Computer-Communications Networks]: Distributed Systems; C.4 [Performance of Systems] General Terms Measurement Keywords Peer-to-peer, Gnutella, Topology