Volumetric displays possess a number of unique properties which potentially make them particularly suitable for collaborative 3D applications. Because such displays have only recently become available, interaction techniques for collaborative usage have yet to be explored. In this paper, we initiate this exploration. We present a prototype collaborative 3D model viewing application, which served as a platform for our explorations. We outline three design goals, discuss the key interaction issues which were encountered, and describe a suite of new techniques in detail. In initial user observation sessions, we found that our techniques allowed users to successfully complete a variety of 3D tasks. Furthermore, interviews with experts in potential usage domains indicated that the techniques we developed can serve as a baseline for future collaborative applications for volumetric displays. Author Keywords Volumetric displays, collaborative interaction. ACM Classification Keywords H.5.2 [Us...