The combination of mobile computing and collaborative Augmented Reality into a single system makes the power of computer enhanced interaction and communication in the real world accessible anytime and everywhere. This paper describes our work to build a mobile collaborative Augmented Reality system that supports true stereoscopic 3D graphics, a pen and pad interface and direct interaction with virtual objects. The system is assembled from off-the- shelf hardware components and serves as a basic test bed for user interface experiments related to computer supported collaborative work in Augmented Reality. A mobile platform implementing the described features and collaboration between mobile and stationary users are demonstrated.