In 2005 the National Animal Health Monitoring System conducted a survey in 183 live poultry markets throughout the United States. The objectives of this study were to describe characteristics of live poultry markets in the United States and to identify potential risk factors for markets to be repeatedly positive for low-pathogenicity avian influenza virus (LPAIV) H5/H7. A questionnaire was administered to market operators that included questions regarding types of birds and other animals in the market, biosecurity, and cleaning and disinfecting practices. A history of testing for avian influenza from March 2004 through March 2005 was obtained for each market. Cases were defined as markets with at least 2 positive LPAI/H5/H7 test results during the year (separate occasions), and controls were defined as markets that were tested at least twice during the year with all negative results. Markets in the North region (New York, New Jersey, Pennsylvania, New England) were larger than markets in the South (Florida, California, Texas) and were more likely to slaughter birds on-site. Testing for avian influenza virus (AIV) was performed more frequently in the North region than in the South region. Markets in the North region tested positive for H5 or H7 at 14.6% of the testing visits, and no markets in the South region tested positive for H5/H7 at any time during the year. Factors associated with repeated presence of LPAIV H5/H7 included number of times the market was cleaned and disinfected, being open 7 days per week, and trash disposal of dead birds.