Data on demographic and clinical characteristics of each patient were collected using the CDC's TB case report form. The relative risk of TB in nursing homes and correctional facilities was estimated by comparing observed (institutional) with expected (community) TB incidence rates. During the 2-year study, 44,456 TB cases were reported in the United States; the 29 States reported 15,379 cases, or 34.6 percent of the total. Within the 29 States, completed study forms were available for 14,885 cases, for a response rate of 97 percent. The aggregate TB case rate for nursing home residents was 1.8 times higher than the rate for elderly persons living in the community. The aggregate TB risk among correctional inmates was 3.9 times higher than the risk for persons living in the community. Overall, findings indicated that excess risk of TB associated with residence in nursing homes and correctional facilities was a widespread phenomenon. Demographic differences between institutional and community populations may have accounted for a significant proportion of the excess risk observed, especially in correctional facilities. Nursing home residents were older and more likely to be female than elderly persons in the community. Correctional inmates were more likely to be male and nonwhite than persons in the community. The authors conclude that considering the unique characteristics of the two institutional populations may provide a basis for developing approaches to prevent and control TB in nursing homes and correctional facilities. 43 references, 7 tables, and 3 figures