In 1991 a major U.S. metropolitan police chief's association identified two key problems that were impeding narcotics enforcement efforts. First, inadequate coordination across a number of local, State, and national agencies had resulted in ineffective investigations and threatened the safety of law enforcement agents. Second, international drug cartels had invested vast resources in advanced information systems designed to keep dealers out of the reach of technologically less-advanced law enforcement agencies. The chiefs, with the assistance of State and national agencies, designed El Centro (a pseudonym), which contained an advanced, computer-based information and collaborative work system intended to promote better coordination of narcotics enforcement efforts within and across jurisdictional boundaries. El Centro has evolved and expanded considerably since its initial formation. This paper traces its development, highlighting the critical moments in its history. Case study methods were used to collect data from documentation, archival records, interviews, and direct observation of training sessions. The authors focus on the two formative phases of the alliance: negotiation and commitment. The paper recounts several potential barriers to the formation of multiagency alliances, including agency diversity, resource limitations, and disincentives to collaboration. It also identifies critical factors for the successful formation of alliances, including common goals, facilitative structural mechanisms, broad participation, and external support. A table lists all the barriers and critical success factors.