To assess the risk of tuberculosis infection in medical and nursing school students, tuberculin skin tests were carried out in the two-step manner. The second tuberculin skin test was repeated two weeks later excluding those who were strongly positive in the first test. BCG vaccination was done with the consent of students who showed negative reaction twice. Medical interview and revaluation of prior routine chest radiogram were made on students who were strongly positive. Prophylactic INH medication was considered to those who are at high risk of tuberculosis. Eight hundred thirty eight students underwent the two-step tuberculin skin test, and among them, 771 students showed the positive reaction on the first test (92.0%) which included 58 weakly positive (6.9%), 347 intermediately positive (41.4%) and 366 strongly positive (43.7%) and 2 not-measurable (0.2%), and 65 students were negative (7.8%). The average size of the erythema was 30.9 +/- 18.8 mm on the first test and 37.9 +/- 20.6 mm on the second test. Twenty one students were negative on the second tuberculin skin test, and among them, 15 received BCG vaccination. Out of eight students who were vaccinated with BCG in 1999 and were followed up in the next year, 6 (75.0%) converted to positive. Strongly positive reaction was seen in 28 students (3.3%) and one of them underwent prophylactic medication of INH according to her family history of exposure to tuberculosis.