Pharmacokinetics of theophylline was studied on 22 asthmatic patients. Aminophylline was administered in dose of 3.6-6.6mg/kg by a single intravenous injection and by a constantrate intravenous infusion for 2 hours. Plasma theophylline concentrations were determined by high-pressure liquid chromatography. In case of single intravenous injection, plasma concentration reached the highest level of 12.7±3.31μg/ml immediately after the injection and, in case of a continuous intravenous infusion, plasma concentratin reached the highest level of 9.1±1.60μg/ml at the end of the infusion. The serial plasma concentration data were analyzed by assuming the 1-and 2-compartment model. In case of a single intravenous injection, the mean plasma theophylline clearance was 0.0517±0.01861 1/kg/hr with k10 0.047±0.076hr-1, α6.689±4.313hr-1, β0.104±0.036hr-1, and V 0.389±0.128 1/kg; in case of a continuous intravenous infusion, they were K0/VK (1-e-KT) 8.91±1.46μg/ml, K 0.120±0.0624hr-1, V 0.437±0.062 1/kg. These data should be useful in determining precise dosage requirements for theophlline therapy of asthma.