In 2001, the DoD identified performance based logistics (PBL) as the preferred weapon system support strategy. Within DoD, PBL is the purchase of performance outcomes, such as system availability, rather than the purchase of individual elements of logistics support -- such as parts, repairs, and engineering support. Although PBL initially arose from efforts to reduce support costs, questions have arisen about whether PBL has reduced support costs as originally intended. This report evaluates the extent to which DoD has used business case analyses to guide decisions related to PBL arrangements and the impact PBL arrangements have had on weapon system support costs. Includes recommendations. Charts and tables.