Metropolitan planning organizations (MPOs) were given significant new responsibilities fo r transportation decision-making with the passage of ISTEA but were exp ected to carry out these responsibilities in partnership with state agencies and a variety of public and private interest groups. Since the ISTEA partnership approach is continued under the fo llow-on TEA-21 /egis/ation, it is important to understand the institutional relationships thus fo rmed and their strengths and limitations. Drawing from the literature as well as our own interviews in two dozen large metropolitan regions, in this paper we review the experience to date with partnerships under JSTEA. Five types of partnerships are identified, in order of increasing levels of interaction, shared responsibility, and role equality: consultation, coordination, cooperation, consensus building, and collaboration. We find that most MPO activities are of the first three types. Successes in lower-level partnerships can open doors for higher levels of partnership, but by no means assure it; partnerships have produced gains but they also have caused cmiflicts. Research on the social learning aspects of partnership development could provide insights into the evolution of regional institutions as well as useful models for progressive practice.