The genetically determined ability to metabolize debrisoquine(DBR) is related to risk of lung cancer and DBR hydroxylation exhibits wide inter-individual variation. In this study, 100 korean adults were tested for their ability to metabolize DBR. The DBR metabolic phonotype were determined by metabolic ratio (MR, DBR/4-HDBR) which is the percent dose excreted as unchanged DBR divided by the percent dose excreted as 4-hydro-xydebrisoqinne(4-HriBR) in a aliquots of an eight hour urine sample, after 10 mg DBR test dose administration. Analysis was performed on a capillary gas chromatography fitted with electron capture detector. The results were as follows; 1. Geometric mean or DBR MR was 0.32 in male, 0.27 in female, 0.30 in total and the distribution of log(MR) was seemed to follow normal distribution. 2. Metabolic ratio of DBR was higher in non-smoker and non-drinker than in smoker and drinker without any statistically significant difference. 3. None of personal factors was significantly related to DBR MR except age. 4. The DBR metabolic phonotype was extensive metabolizer(EM) 93, intermediate metabolizer (IM) 7 by traditional method and EM 98, IM 3 by Caporaso's method. The poor metabolizer (PM) phenotype was not found by either method. 5. Maximal expected PM phenotype was 0.36% by traditional method and 0.04% by Caporaso's method.