This study was conducted to determine the urinary nicotine and cotinine concentration in 126 smokers and 143 nonsmokers. While urine samples were being collected, personal characteristics related to smoking habit such as sex, age, number of years since a person has been a smoker, average number of cigarettes consumed per day, and number of smokers in the family were surveyed. Urinary nicotine and cotinine concentration were analyzed by GC/NPD. The smokers smoked an average 17.0 cigarettes per day and the average concentration of nicotine and cotinine was 3.88 $mu extrm{g}$/ml and 3.64 $mu extrm{g}$/ml, respectively. The average number of smokers in the family was 0.72 persons and the average concentration of nicotine and cotinine were 0.11 $mu extrm{g}$/ml and 0.02 $mu extrm{g}$/ml in the urine of non-smokers, respectively. The concentration of nicotine and cotnine in smoker`s urine was dependent on the number of cigarettes smoked per day(p<0.01). The number of years since a person had been a smoker, and the number of smokers in the family were not associated with the concentration of nicotine and cotinine. Also there was no significant effects of passive smoking on the family of smokers by the level of nicotine and cotinine concentration. We describe the relationship between smoking habit as assessed by urinary nicotine and cotinine excretion. This study provides an evidence for the assessment of active and passive exposure to tobacco smoke.