Mycobacterium tuberculosis is transmitted through the air from an infectious patient (index patient) to other persons (contacts) who share space. Exposure to M. tuberculosis can result in tuberculosis (TB) disease or latent TB infection (LTBI), which has no clinical symptoms or radiologic evidence of disease. The cycle of transmission can be ended by isolating and treating patients with TB disease, examining contacts, and treating LTBI to prevent progression to TB disease. CDC systematically collects aggregate data on contact investigations from the 50 states, the District of Columbia (DC), and Puerto Rico. Data from 2003-2012 were analyzed for trends in yields from contact investigations, in terms of numbers of contacts elicited and examined and the estimated number of TB cases averted through treatment of LTBI among contacts in 2012. During 2003-2012, the number of TB cases decreased, while the number of contacts listed per index patient with contacts elicited increased. In 2012, U.S. public health authorities reported 9,945 cases of TB disease (1) and 105,100 contacts. Among these contacts, 84,998 (80.9%) were examined; TB was diagnosed in 532 (0.6%) and LTBI in 15,411 (18.1%). Among contacts with LTBI, 10,137 (65.8%) started treatment, and 6,689 (43.4% of all contacts with LTBI) completed treatment. By investigating contacts in 2012, an estimated 128 TB cases (34% of all potential cases) over the initial 5 years were averted, but an additional 248 cases (66%) might have been averted if all potentially contagious TB patients had contacts elicited, all contacts were examined, and all infected contacts completed treatment. Enhancing contact investigation activities, particularly by ensuring completion of treatment by contacts recently infected with M. tuberculosis, is essential to achieve the goal of TB elimination.