Tuberculosis is a main cause of mortality and morbidity in developing countries. Although diagnostic and curative means are well known, they are not always available and affordable. Also, the disease has a worldwide stigma, which adds to the suffering. A survey exploring the correlates of prejudice, as an attitudinal component of this stigma, was carried out in Cali, Colombia. Results show that scientifically unfounded beliefs about the transmission of the disease are the main significant predictor of the instrumental function of this attitude. Health education and, arguably, more successful control programmes could help to reduce the social isolation suffered by people with tuberculosis.