To evaluate pharmacokinetic parameters and maintenance dose of theophylline in Korean adult asthmatics, we estimated total body clearance by nonlinear computer analysis according to age and sex after continuous infusion of aminophylline in 82adult asthmatics (age range 20-81 years old). Eight men were smokers. In nonsmoking male and female patients, the total body clearance of patients over 55years old was significantly lower than that of patients under 55years old(p<0.05). In nonsmoking male patients, the total body clearance was 44.2±9.9 ml/hour/kg in patients under 55years old and 33.2±8.2 ml/hour/kg in patents over 55years old. In nonsmoking female patients, it was 44.1±13.6ml/hour/kg in patients under 55years old and 34.1±8.2 ml/hour/ kg in patients over 55years old. The regression equations between total body clearance and age were total body clearance (ml/hour/kg)= 0.403×Age+59.698 in male (r=0.50, p<0,05) and 0.546×Age+67.462 in female (r=0.61, p<0.05). The total body clearance of smoking male was increased by 27% compared to that of nonsmokers of same age group. There was no significant diference between clearance of Korean adult asthmatics and that of western people reportec1 by Hendeles and Antal. And there was no difference according to gender in same age groups. Even though we can calculate serum theophylline concentration from above equations, variability of total body clearance is so wide that regular estimation of serum theophylline concentration is recommended.