Commisioning is a quality assurance process for buildings from predesign through design@ construction@ and operations. It involves achieving@ verifying@ and documenting the performance of each system to meet the building?s operational needs within the capabilities of the documented design and equipment capacities@ according to the owner's functional criteria. Commissioning includes preparing project operational and maintenance documentation and training operation and maintenance personnel. The result should be fully functional systems that can be properly operated and maintained throughout the life of the building. This chapter gives an overview of the general commissioning process@ plus best practices from the May 2002 working draft of ASHRAE Guideline 0-200X@ The Commissioning Process@ developed for the National Institute of Building Sciences? total building commissioning program. This chapter generally provides less detail and is less prescriptive@ but provides more narrative discussion on some issues than the cited commissioning guideline draft.