A cross-sectional study was done at the University of Antioquia Medellin Colombia to evaluate the response to a tuberculin skin test among students in undergraduate health programs (medicine odontology nursing and bacteriology) as compared to undergraduate students in non-health programs. The study included students from the beginning middle and end of the universitys academic programs. The sample of 490 students included 273 from health programs and 217 from non-health programs. Participants were randomly selected using lists provided by the university registrar for the second semester of 1998. The presence of a Bacillus Calmette-Guerin (BCG) vaccination scar was determined and all the participants were also questioned about tuberculosis-related risk factors. Tuberculin skin test reactivity was evaluated by the size of induration 72 hours after intradermal injection of two tuberculin units of purified protein derivative RT 23. There were no differences in tuberculin reactivity between students from the health programs and from the non-health programs irrespective of the academic level. However there was a significantly higher proportion of positive skin tests among students with a BCG scar. These results suggest that undergraduate health students do not have extensive contact with TB patients or with clinical samples from such patients. Nevertheless the results do not rule out TB as an occupational risk for health personnel. (authors)