This is the fourth report in a series of publications presenting estimates of the percentage of eligible persons, by State, who participate in the Food Stamp Program (FSP). This issue presents food stamp participation rates for States in September 1999 and the change between September 1994 and September 1999. This information can be used to assess recent trends in program performance and focus efforts for improvement. This report also presents revised estimates of FSP participation rates for States in September of 1994 to 1998. These estimates differ from those previously reported because of improvements in data and estimation methods.