In this paper the notion of collective intention in teams of agents involved in cooperative problem solving (CPS) in multiagent systems (MAS) is investigated. Starting from individual intentions, goals}, and beliefs defining agents' local asocial motivational and informational attitudes, we arrive at an understanding of collective intention in cooperative teams. The presented definitions are rather strong, in particular a collective intention implies that all members intend for all others to share that intention. Thus a team is created on the basis of collective intention, and exists as long as this attitude between team members exists, after which the group may disintegrate. For this reason it is crucial that collective intention lasts long enough. Collective intentions are formalized in a multi-modal logical framework. Completeness of this logic with respect to an appropriate class of Kripke models is proved. Two versions of collective intentions are discussed in the context of different situations. It is assumed that these definitions reflect solely vital aspects of motivational attitudes, leaving room for case-specific extensions. This makes the framework flexible and not overloaded. Together with individual and collective knowledge and belief, collective intention constitutes a basis for preparing a plan, reflected in the strongest attitude, i.e., in collective commitment, defined and investigated in our other papers.