Ketorolac tromethamine (KT) is a non-steroidal drug with potent analgesic and anti-inflammatory activity and is absorbed rapidly (T-max (1.0h) with an efficiency >87% following oral and intramuscular administration. The plasma half-life of ketorolac ranges from 1.1 to 6.0 h. Its oral bioavailability is estimated to be 80%. Ketorolac has been found 36 times more potent than phenylbutazone, approximately twice as potent as indomethacin, and three times more potent than naproxen in suppressing carrageenan-induced paw oedema in rat. In this study, microcapsules of KT were prepared by means of coaceruation-phase separation technique induced by the addition of non-solvent, and release rates from microcapsules were studied. Eudragit S100 was used as the coating material. Coacervation was achieved by the addition of cyclohexane at 2 ml/min at 25 degrees C and 1:4 solvent:non-solvent ratio was used. The microcapsules were washed with cyclohexane to harden the wall and dried at room temperature. Microcapsules with core:wall ratio of 1:1 and 1:2 were prepared and the particles obtained by sieving with an average diameter of 177-500 mu m were used. The yield was calculated and the release properties of KT were investigated by USP XXII paddle method and using UV spectrophotometry at 318 and 323 nm.