Levetiracetam is a unique anticonvulsant drug that has been used effectively in humans and shows promise in canine patients. The pharmacokinetics have been determined and safety evaluated in humans, dogs, rodents and rabbits with no apparent side effects at recommended dose regimens. The purpose of this study was to determine if therapeutic concentrations of levetiracetam can be achieved and maintained throughout a reasonable dosing interval (either orally or intravenously) at doses not associated with adverse effects in the cat. The study design was a prospective, randomized, double cross-over. Ten healthy purpose-bred cats were administered levetiracetam (20 mg/kg) either orally or intravenously. Blood was collected at times 0, 10, 20, 40 minutes, 1, 1.5, 2, 3, 4, 6, 9, 12 and 24 hours. Plasma levetiracetam concentrations were determined by high performance liquid chromatography and expressed as mean ± standard deviation. No adverse events were noted during the course of the study. Mean (± sd) values were: peak concentration (mcg/ml) 25.54±7.97 (oral Cmax) and 37.52±6.79 (IV C0), elimination half-life (hr) 2.95±0.95 (oral) and 2.86±0.65 (IV), mean residence time (hr) 5.65±1.25 (oral) and 4.57±0.94 (IV), apparent volume of distribution (L/kg) 0.52±0.09, clearance (ml/kg/min) 2.0±0.60. The oral bioavailability (%) was determined to be 100±0.39. Drug concentrations were in the therapeutic range determined for humans (5-45 mcg/ml) for at least 9 hours. Based on these results, a 20 mg/kg oral or IV dose of levetiracetam every 8 hours in cats is expected to result in plasma concentrations within the therapeutic range established for humans. This study supports the use of levetiracetam as an alternative anti-epileptic drug in cats; however further studies are indicated to evaluate the efficacy of levetiracetam in seizure management in this species.