Intraventricular injection of DL-kynurenine and L-kynurenine sulfate (40 .mu.g) into conscious mice potentiated convulsions and lethality produced by strychnine (1 mg/kg) and not by thiosemicarbazide nor pentylenetetrazol. Another metabolite of tryptophan with convulsive effect, quinolinic acid, was ineffective. Injection (i.p.) of DL-kynurenine sulfate and quinolinic acid (25-100 mg/kg) was associated with prolongation of the latency of strychnine and thiosemicarbazide (only the former drug) seizures. Nicotinic, picolinic and anthranilic acids (100 and 250 mg/kg) did not modify the action of convulsants. Data and suggestions about probable involvement of brain glycine and GABA receptors in the convulsive action of kynurenines is discussed.