As part of a larger study, this analysis, first, uncovers a previously alluded to, but heretofore un-explicated, phase of project team development (PTD) -- dubbed mobilization and launch -- and, then, explores the ways in which activities and outputs of this phase relate to project team effectiveness (PTE) by comparing them across three high and three low performing teams. The analysis shows that the former used this formative period: (1) to actuate a comprehensive mobilization strategy that was carried out relatively rapidly and resulted in well informed, as well as fully and competently staffed, teams and (2) to hold highly participatory launch meetings from which team members emerged in general agreement about what needed to be done and how and by whom it would be done. Low performing teams, in contrast, basically squandered this potentially valuable time and, thus, emerged from this phase totally unprepared to move to and effectively through subsequent phases of PTD.