. The hypothesis of this study is that, because of infection with the human immunodeficiency virus (HIV), homelessness and a variety of other social and medical factors, increasing proportions of cases of tuberculosis in San Francisco are the result of recent infection with Mycobacterium tuberculosis. It is postulated that these infections are acquired from identifiable sources within the community and that the sites wherein transmission of M. tuberculosis takes place can be determined. This proposal describes a community-based study in which restriction fragment length polymorphisms (RFLP) pattern analysis will be utilized in combination with intensive epidemiologic investigation to describe the distribution and dynamics of urban tuberculosis. This Study will utilize RFLP to identify clusters of cases having tuberculosis caused by the same strain, the assumption being that clustering indicates recent infection with rapid progression to disease. Thus, determining the proportion of cases in clusters would be an indicator of the number of infectious sources in the community. The questions that are sought to be answered are as follows: What is the relative proportion of the total tuberculosis cases in San Francisco who are in clusters? How do the characteristics of cases in clusters differ from noncluster cases? Can unsuspected sites and, perhaps, patterns of transmission of M. tuberculosis be identified? What are the relative contributions of health care facilities, correctional institutions, and migration to the incidence of tuberculosis in San Francisco? Can RFLP pattern analysis be useful in evaluating the adequacy of a tuberculosis control program? This study is a prospective, community-based examination with both descriptive and comparative components. The intent is to include all patients in San Francisco with newly diagnosed tuberculosis. Isolates of M. tuberculosis from all patients who have new diagnosis of tuberculosis, as well as any isolates obtained four or more months after the diagnosis, will undergo RFLP analysis. Pattern matches will be sought using an automated scanning system. After collection of the epidemiologic data is complete the RFLP data files will be linked to the epidemiologic and clinical data that will be maintained in the same computer. Analyses will be directed toward analyzing changes in cluster numbers and distribution over time, examination of clusters to track disseminators and comparisons of different variables in persons in and not in clusters, and determination of the benefits of RFLP on evaluating contact investigation procedures.