This paper presents a new database transaction manager, CADTM, for coordinating design activities in CAD environments. Unlike the previous approaches for coordinating design activities, in which each designer faces complexity of a design activity, CADTM encapsulates the complexity of design activities from designers. This is achieved by the notion of transaction template which guides the designer not to produce incorrect design results due to misunderstanding of complex design activities, and by the notion of interleaving specification which enables the designer to cooperate with his/her group members in a consistent way. In CADTM, therefore, any designer does not need to know the details of the design activity, and also does not need to concern whether he can release intermediate results of a transaction.