A survey was conducted in 1988 to estimate the prevalence of respiratory symptoms and pulmonary tuberculosis in people over age 15 in the Northeast Sector of Medellín, Colombia, an area suffering from severe socioeconomic depression. A cluster sample was selected for this purpose and 3,731 adults were interviewed in their homes. Those classified as respiratory symptomatics (ones reporting a cough lasting two weeks or more) were asked to provide samples for three sputum-smear examinations. The prevalence of pulmonary tuberculosis found in this survey was 2.68 cases per 1,000 subjects, a rate substantially greater than the prevalence of tuberculosis cases recorded in the Northeast Sector, and the prevalence of respiratory symptomatics was 70 per 1,000 subjects. Of eight subjects whose cases had been diagnosed previously, three said they had abandoned treatment. The prevalence of respiratory symptomatics was higher among poorly educated subjects and among those sleeping in poorly ventilated and/or overcrowded quarters. Overall, the survey data suggest that the tuberculosis control program in Northeast Medellín confronts a spectrum of problems ranging from low case-detection rates and high rates of abandoned treatment to social conditions and behavior patterns that foster host vulnerability and disease transmission.