A water extract of the West African black pepper Piper guineense L. was tested for activity against audiogenic seizures in DBA/2 mice, and against seizures induced in T.O. mice by N-methyl-DL-aspartate (NMDLA), pentylenetetrazole (PTZ) and maximal electroschock. Single intraperitoneal doses of the extract produced significant protection of DBA/2 mice against audiogenic seizures. The highest of three doses tested produced 100% and 58% protection at 6 h and 18 h after treatment, respectively. The extract also protected T.O. mice against convulsions induced by NMDLA and maximal electroshock but it had no significant effect on PTZ-induced convulsions. The doses of the extract tested did not cause significant impairment of performance of T.O. mice on a rotarod test. The results indicate that the extract of P. guineense has prolonged anticonvulsant activity at doses which do not cause significant CNS depression.