The anticonvulsant activity of the novel drug D-23129 (N-(2-amino-4-(4-fluorobenzylamino)phenyl)carbamic acid ethyl ester) was evaluated in animal models of epileptic seizures. D-23129 was active after oral and intraperitoneal administration in rats and mice in a range of anticonvulsant tests at nontoxic doses. The compound was active against electrically induced seizures (MES, ED50 rat p.o. = 2.87 mg/kg), against seizures induced chemically by pentylenetetrazole (s.c. PTZ, ED50 mouse p.o. = 13.5 mg/kg), picrotoxin and N-methyl-D-aspartate (NMDA) and in a genetic animal model, the DBA/2 mouse. It was not active against seizures induced by bicuculline and strychnine. Motor impairment, evaluated with the rotarod test and by observation in the open field, was minimal at doses showing anticonvulsant activity. D-23129 was very effective in elevating the threshold for electrically and chemically induced seizures. Considering the dose increasing the MES threshold by 50% (TID50 mouse i.p. = 1.6 mg/kg; TID50 rat i.p. = 0.72 mg/kg) and the TD50 obtained in the rotarod test, the protective index of D-23129 is better than that of valproate and phenytoin. During 14 days chronic oral treatment with 15 mg/kg, no development of tolerance was observed. D-23129 thus presents an orally active, safe, broad spectrum anticonvulsant agent, which is structurally unrelated to anticonvulsants currently used. We expect that D-23129 will improve the treatment of refractory seizures in humans.