Summary: Cattle and hog producers have raised concerns about changes in their industries that affect competition, such as mergers among meatpacking companies, increased marketing of livestock through contracts, and greater control by meatpacking companies over livestock production and marketing. Under the Packers and Stockyards Act, the U. S. Department of Agriculture (USDA) is responsible for monitoring the cattle and hog industries and halting unfair and anticompetitive practices. USDA has assigned this responsibility to the Grain Inspection, Packers and Stockyards Administration (GIPSA). Because of continued concerns about whether GIPSA is adequately protecting competition in the livestock markets, GAO reviewed USDA's efforts to implement the Packers and Stockyards Act. This report discusses the number and status of investigations conducted by GIPSA in response to complaints about anticompetitive activity and factors that affect GIPSA's ability to investigate concerns about anticompetitive practices. GAO recommends several actions to improve GIPSA's investigations, including integrating USDA attorneys into GIPSA's investigative teams and adopting more systematic approaches to its investigative work. GAO summarized this report in testimony before Congress; see: Packers and Stockyards Programs: Investigations of Competitive Practices Need Improvements by Lawrence J. Dykeman, Director of Food and Agriculture Issues, before the Subcommittee on Administrative Oversight and the Courts, Senate Committee on the Judiciary. GAO/T-RCED-00-299, Sept. 24 (13 pages).