Outcome for bipolar disorder remains suboptimal despite the availability of efficacious treatments. To improve treatment effectiveness in clinical practice, a Veterans Affairs study team created a care model conceptually similar to the lithium clinics of the 1970s but augmented by principles of more recent collaborative care models for chronic medical illnesses. This intervention consists of improving patients' self-management skills through psychoeducation; supporting providers' decision making through simplified practice guidelines; and enhancing access to care, continuity of care, and information flow through the use of a nurse care coordinator. In this article, which is part I of a two-part report, the authors summarize the conceptual background and development of the intervention, describe the design of a three-year, 11-site randomized effectiveness trial, and report data describing its successful implementation. Trial design emphasized aspects of effectiveness to support generalizability of the findings and eventual dissemination of the intervention. Part II (see companion article, this issue) reports clinical, functional, and overall cost outcomes of the trial.