The purpose of this article is to describe an important aspect of organizing a Networked Improvement Community (NIC) by a large national effort, namely, the role of leadership structures. The article analyses a case study of the formation of a particular NIC, the Mathematics Teacher Education Partnership (MTE-Partnership). Six factors were identified as particularly important: convening the network, development of a membership framework, development of participation structures, building the leadership and hub functions of the partnership, development of an effective infrastructure for communications and developing human and material resources needed for the partnership to function effectively.