With the federal role in education changing rapidly, regional education agencies are best suited to engage in school improvement efforts by designing cooperative arrangements among other educational organizations. Although planning such a collaborative interorganizational relationship (IOR) seems to require both appropriate structures among member organizations and methods of communication that encourage shared decision-making, a sample of IOR's in Massachusetts shows that the interaction processes were of more importance than organizational structures in determining a collaborative relationship. The type of coordinating structure chosen for an IOR depends largely on the extent of school system input in the decision-making process. Although resources available to member organizations can also be coordinated to save money and improve service, such cooperation requires clearly specified units of exchange and terms of reciprocity. Moreover, each organization's domain must be specified in problem-solving activities of collaborative IOR's. (JW)