In this paper, a new type of interaction environment, the multiscale collaborative virtual environment (mCVE), is proposed to support multiple users working together at different scale levels. This paper introduces the concept of multiscale collaboration in the context of 3D virtual environments and describes the benefits of multiscale collaboration for understanding and managing large structures that present important features at different scale levels. After a discussion on the design and implementation of multiscale tools to support the visualization of structures, cross-scale information sharing, and cross-scale action, the paper presents an experimental study showing that cross-scale collaboration can improve user performance.