L-Deprenyl (selegiline), a selective inhibitor of monoamine oxidase type B, has recently been shown to exert anticonvulsant and antiepileptogenic effects in the kindling model of partial (focal) epilepsy. In the present study, we examined if L-deprenyl exerts anticonvulsant effects in standard rodent models of generalized seizures. In addition to anticonvulsant activity, behavioral effects induced by L-deprenyl were monitored closely. To assess the stereoselectivity of anticonvulsant and behavioral effects of deprenyl, the D-enantiomer was included in the studies. Furthermore, the antiepileptic drug phenobarbital was used for comparison. The following tests were performed in mice: 1) the threshold for tonic electroconvulsions; 2) the maximal electroshock seizure test with fixed supramaximal (suprathreshold) stimulation; 3) the threshold for myoclonic, clonic and tonic seizures in response to i.v. infusion of pentylenetetrazole (PTZ); 4) the s.c. PTZ seizure test, with a fixed dose of PTZ (80 microgram/kg) for seizure induction; 5) the rotarod and chimney tests for determination of motor impairment. Furthermore, animals were observed in cage and open field for stereotyped behavior and other behavioral abnormalities. L-Deprenyl, tested at doses of 1 to 40 microgram/kg i.p., significantly increased myoclonic and clonic PTZ thresholds and the threshold for tonic electroconvulsions, whereas D-deprenyl was either ineffective or exhibited a lower anticonvulsant potency than L-deprenyl. Both drugs were ineffective in the maximal electroshock seizure and s.c. PTZ seizure tests. In contrast to the higher anticonvulsant potency of L-deprenyl in seizure threshold tests, D-deprenyl was more potent than L-deprenyl to induce behavioral abnormalities, such as hyperlocomotion. The data indicate that L-deprenyl exerts anticonvulsant activity against different seizure types. This anticonvulsant activity and the previously reported neuroprotective and cognition-enhancing action of L-deprenyl offer a unique combination of drug effects which might be of clinical benefit in patients with epilepsy.