The current network environment is composed of heterogeneous H/W and S/W resources. Integrating CSCW applications in such heterogeneous environments is highly complex. This paper describes the design and implementation of ASS (application sharing server) which supprot sharing of a single application between different operating systems. The ASS supports cooperative work among user group using its own window system (X-windwo or MS-windwos). We adopted improved managing heavy-weight data. ASS also provides development environment for vaious groupware application.