Evaluating the implementation of Total Maximum Daily Loads (TMDLs), especially their ultimate effects on water quality, is challenging but important. It is needed to reveal whether a TMDL and implementation actions are working or should be revised. It also provides information about restoration and protection, ideally making future efforts more effective and efficient, and it helps to demonstrate to the public the impact of TMDL programs and other Clean Water Act programs. This report highlights the diversity of approaches to evaluating the water quality effects of TMDL implementation, explains some of those methods, and conveys lessons learned. It also details terminology challenges and identifies relevant resource materials. The objective of the document is to facilitate communication among water quality programs, especially TMDL programs, and help generate new ideas in this underexplored area.