Abstract. We present a form of case-based reuse conducive to the cooperation of multiple CBR agents in problem solving. First, we present a form of constructive adaptation for configuration tasks with compositional cases. We then introduce CoopCA, a multi-agent constructive adaptation technique for case reuse. The agents suggest possible components to be added to the ongoing configuration problem, allowing an open, distributed process where components used in cases of different agents are pooled together in a principled way. Moreover, the agents can use their case base to inform about a similarity-based likelihood that the suggested component will be adequate for the current problem. We illustrate CoopCA by applying it to the task of agent team formation1 .