In Korea BCG vaccination has been employed as the main control measure for tuberculosis since 1962. Recently, the protective efficacy of BCG against tuberculosis has been controversial worldwide. A case-control study was conducted to evaluate the efficacy of BCG in Korea which has a high prevalence of tuberculosis(2.5%). The study subjects were children under the age of 14 years who were hospitalized and diagnosed as tuberculosis in three general hospitals in Taegu City during last 6 years ($1975{sim}1980$). Among 416 hospitalized tuberculous patients, 314 cases were confirmed as to the presence or absence of the BCG scar. A control group was selected from the same hospital patients of the same period as the cases. The control group was other than tuberculous patients whose distribution of age, sex and residence were the same as the cases. The results obtained are as follows: For all forms of tuberculosis, the relative risk and the protective efficacy of BCG were 3.5 and 71.8%. The efficacy was higher among female than among male (78.6% vs. 65.8%). The efficacy was higher among the one year and above than among less than 1 year of age. For tuberculous meningitis, the relative risk and the protective efficacy of BCG were 3.9 and 74.3 %. The efficacy was statistically significantly higher among female than among male (p<0.05). The relative risk and the protective efficacyt of BCG for uberculous meningitis combined with miliary tuberculosis and combined with pulmonary tuberculosis represented 6.9, 85.6%, and 7.4, 86.5%, respectively. On the other hand, the relative risk and the protective efficacy of BCG for miliary tuberculosis were 2.1 and 51.6%, and for pulmonary tuberculosis, 2.3 and 54.7%, respectively. From these results, it appears that BCG vaccination is an efficient preventive measure in Korea where tubercluosis is prevalent. Thus the routine BCG vaccination should be continued.