Abstract: This paper deals with the formulation, preparation and evaluation of sustained-release theophylline tablet (SRTT) by measuring in vitro/in vivo release. The serum levels of theophylline in 12 healthy adult volunteers after oral administration of SRTT were determined by a modified UV spectrophotometric method. The pharmac0kinetic parameters were fitted by non-linear least square method with Sharp PC-1211 pocket-computer on the basis of one compartment model. The result showed that the therapeutic serum levels after single dose of SRTT (300 mg) appeared at 3.8 h and maintained over 5 μg/ml for up to 23 h, while that of multiple dose of SRTT (300 mg/every 12 h)appeared at 3 h and reached steady state (13.78±0.47 μg/ml) on the third day.By comparing the pharmacokinetic parameters between SRTT and an imported sustained-release product (Theo-Dur), a good bioequivalence was demonstrated. The correlation between dissolution rates and serum levels was mathematically treated by deconvolution method, and the calculated theoretical values was consistent with the observed data.