We report a microepidemic of tuberculosis (TBC) in a family of 12 members, 4 of which were parenteral drug abusers and 3 had anti-human immunodeficiency virus (HIV) antibodies. Four new cases were simultaneously diagnosed in the investigation of the contacts of a patient with extrapulmonary tuberculosis and acquired immunodeficiency syndrome. We review the requirements for the development of these epidemic outbreaks, both in noninfected communities and in the family contacts, where positive anti-HIV antibodies may increase the risk. We emphasize the importance of a systematic study of contacts in these families and the indication of chemoprophylaxis in all those sharing the same household, without age limit.