Purpose. This study investigates and identifies the determinants of effectiveness within mandated One-Stop employment and training networks. Key within this analysis is the role of leaders and the relevance of leadership attitudes, aptitudes, and activities in engendering cooperation, coordination, and true collaboration. Theoretical framework. The theoretical framework for this study is based on both systems and leadership theories. Each has been adapted to accommodate the nature of collaboratives and, in particular, mandated networks. Methodology. This study utilizes a cross-case comparison analysis. Data collection, both first and secondary was gathered from 10 sites in 2003-2004 within Los Angeles County. Questions of leadership style, network development, and collaborative governance were highlighted. Findings and conclusions. This study offers preliminary evidence that network effectiveness can be attributed to the integration strategies and systemic changes brought about by those in leadership and influence positions within collaborative networks. The data supported the contention that the differences between effective and non-effective workforce investment boards can be explained by the role which leaders play in controlling and channeling the means and activities that drive their collaborative agendas forward. Recommendations. Key in this analysis and critical in a comprehensive understanding is what motivates individuals and agencies to come and work together. As explored in this study, collaborations are complicated and often conflictual. This is even more so under mandated directives. Given this, leaders not only have a vital role but a veritable responsibility in developing the framework and fostering the evolvement of effective collaborative endeavors. Critical toward this end, is the need to properly prime and prepare collaborative leaders to assume this role.