A survey was conducted in 1988 to estimate the prevalence of tuberculosis and respiratory disease (cases of tuberculosis and patients with respiratory symptoms who tested negative for the presence of bacilli) in persons over the age of 15 and of low socioeconomic status in the northeastern commune of Medellín. A cluster sample was selected and 3,731 adults were interviewed. The interviews were carried out in the interviewees' homes. For those patients classified as having respiratory symptoms (two weeks with cough, without considering other symptoms), samples of sputum were taken and a series of three examinations for bacilli were performed in order to confirm the diagnosis. When the interviewee could not be located, the material for collection of samples was delivered to family members. The prevalence of tuberculosis was estimated to be 2.68 per 1,000 population, and that of respiratory disease, 70 per 1,000 population. Of those who initiated treatment, 37.5% abandoned it. The prevalence of respiratory disease was higher among persons who did their cooking and sleeping in the same room, those living in poorly ventilated and overcrowded dwellings, and those with the fewest years of schooling.