States with fewer than 3.5 cases of tuberculosis (TB) per 100,000 population are designated as states with low incidence for TB, corresponding to CDC's interim target rate for 2000, with a goal to eliminate TB in the United States by 2010. Indiana is a low-incidence state, with a TB case rate of 2.3 per 100,000 population in 2003. However, during 2000-2002, Allen County, Indiana, exceeded the state TB case rate with a mean case rate of 2.9 (range: 2.7-3.0) per 100,000 population. The TB case rate in Allen County increased to 4.7 per 100,000 population (with 16 patients reported with TB disease) in 2003 and to 7.0 per 100,000 population (with 12 patients reported with TB disease) during the first half of 2004. The Allen County Department of Health (ACDH), the Indiana State Department of Health, and CDC are investigating this ongoing TB outbreak. This report describes the preliminary results of the investigation, the efforts of ACDH to restructure its TB program, and the importance of maintaining TB-control efforts in low-incidence states.