Objectives. We assessed if HIV testing and diagnoses increased during the week of National HIV Testing Day (NHTD) and if characteristics of people who were tested varied compared with control weeks.Methods. We analyzed HIV testing data from the 2010 National HIV Prevention Program Monitoring and Evaluation system to compare NHTD week (June 24-30, 2010) with two control weeks (January 7-13, 2010, and August 12-18, 2010) for the number of HIV testing events and new HIV-positive diagnoses, by demographics and other HIV-related variables. Characteristics associated with testing during NHTD week compared with control weeks were identified using Chi-square analyses.Results. In 2010, an average of 15,000 more testing events were conducted and 100 more new HIV-positive diagnoses were identified during NHTD week than during the control weeks (pϽ0.001). Compared with control weeks, people tested during NHTD week were significantly less likely to be aged 20-29 years and non-Hispanic white and significantly more likely to be (1) aged Ն50 years, (2) non-Hispanic black or African American, (3) men who have sex with men, (4) low-risk heterosexuals, (5) tested with a rapid HIV test, or (6) tested in a non-health-care setting.Conclusion. In 2010, CDC-funded HIV testing events and new HIV-positive diagnoses increased during NHTD week compared with control weeks. HIV testing programs increased the use of rapid tests and returned a high percentage of test results. NHTD campaigns reached populations disproportionately affected by HIV and further expanded testing to people traditionally less likely to be tested. Incorporating strategies used during NHTD in programs conducted throughout the year may assist in increasing HIV testing and the number of HIV-positive diagnoses.