The tuberculin skin test is an important aid in the detection of tuberculosis especially in child-centered approach to tuberculosis control. The Monotest and the Mantoux test were performed and B.C.G. vaccination coverage rate was assessed. A total of 139 kindergarten children in Seoul and 89 public nursery children in rural area were subjected to the tests. Each child was incoculated simultaneously to one side arm with purified protein derivative(PPD, 5u) and to another aide arm with monovacc(Institut Merieus). Results from each test were read separately and independently 72 hours after administration. At the same time B.C.G vaccination scar size was measured. B.C.G. vaccination coverage rate was 20.9% in urban area, and 15.7% in rural area. When induration of 2mm or greater was considered a positive Monotest reaction and compared to a positive Mantoux reaction of 10mm or greater, the sensitivity of Monotest to Mantoux test was 100% and the specificity was 89.29%. When induration of 5mm or greater was considered a positive Monotest reaction and compared to a positive Mantoux reaction of 10mm or greater, the sensitivity of Monotest to Mantoux test was 81.25% and the specificity was 98.9%. From these results I would assume that the Monotest can be substituted for Mantoux test as screening test, especially in preschool aged children who are apt to be fearful of needles used in the Mantoux test, and rather impatient. As screening test, 2mm or greater induration of Monotest is considered to be preferable to 5mm or greater as a positive result. All children with doubtful or positive reactions to a Monotest should be retested using the Nantoux technique because of relative highfalse positive rate.