Though collaboration is often required in community initiatives, little evidence documents relationships between collaboration and program success. The authors contend that clarification of the construct collaboration is necessary for investigating its contribution to the success of community initiatives. After respecifying collaboration, they present a study of a multisite program that involved varying degrees of collaboration in the 16 communities adopting a nurse home visitation program. The authors employ hierarchical linear modeling (HLM) to test the predictive power of individual participant characteristics and examine the increased accuracy of predictions from a second level model of site qualities--specifically, features of the collaborative process associated with different sites. The first-level model predicted approximately 10% of the variance in attrition, or dropout, of program clients. The second-level model accounted for an additional 28% of the variance in attrition. A theory of commitment transfer is offered as a first explanation of this result. (Contains 5 tables.)