Conference system support commuication and collaboration among geographically dispersed user groups. In our contribution we introduce SketchPad, a multi-user freehand sketching system, particularly designed for the use within a conference with geographically divided users. In the future, most product prototyping work will be done on computers with all-digital data bases, interfaces, and output. The emphasis on concurrent engineering, total quality management, manufacturability, just-in-time manufacturing, and life-cycle costing makes prototyping a group collaborative effort. Similarly, the emphasis on virtual enterprises that span the world with their customers and suppliers make prototyping a truly distributed activity.