A longitudinal study of the process of planning and implementing an inservice program in a large urban school district was conducted. After extensive interviews with participants, a premise that collaborative planning contributes to the successful implementation of an innovation emerged. This method of planning is characterized by project plans that are made with equal input from the project managers (the Top) and the persons whose behavior is to be changed (the Grassroots). Throughout the egalitarian planning effort, all layers of participants in the change process are jointly involved in decision making, and each enjoys an equal share of planning power. Collaborative planning can appear in yet another form, "dialectical collaboration". This is distinguished by an integration of directives from the Top, Grassroots action, and joint planning. Impetus for change may come from the Top or the Grassroots, and collaborative planning implements the change. The implications of these findings for developing large-scale inservice programs successfully are discussed. (JD)