Ketrorolac tromethamine (KT), a nonsteroidal anti-inflammatory drug (NSAID) is required repeated administration due to its short blood half-life. To avoid dose-dependent side effects of KT, sustained-release pellets containing KT were prepared by coating with Eudragit$^{(R)}$ RS 100 and Eudragit$^{(R)}$ NE 30D. The in vitro and in vivo drug release behavior of KT from Eudragit$^{(R)}$ RS 100 and NE 30D coated pellet (SR-A), Eudragit$^{(R)}$ RS 100 coated pellet (SR-B) and conventional commercial immediate-release tablet (IR) was investigated. KT from SR-A and SR-B was slowly released over several hours, whereas IR showed rapid initial release in vitro. The pharmacokinetic study in vivo was performed by oral administration in beagle dogs. 5 mg IR was administered 3 times at intervals 5 hr. Five milligrams of IR was administered 3 times at intervals of 5 hr and 15 mg of SR-A and SR-B did once. After administering IR, KT concentration in blood showed high peak- trough fluctuation and stomach ulcer were discovered. On the other hand, SR-A and SR-B sustainedly released KT and reduced the occurrence of stomach ulcer. There sustained-release pellets will be effective system to minimize dosedependent of side effect and improve patient compliance.