The action of progabide against motor seizures elicited by pentylenetetrazol was studied in 7-, 12-, 18-, 25-day-old and adult rats. Progabide (dissolved in dimethylsulfoxide) was injected in doses from 12.5 to 150 mg/kg i.p. 30 min before pentylenetetrazol. Minimal seizures were not affected by solvent or progabide pretreatment. The action of progabide against major, i.e. generalized tonic-clonic seizures, changed with age: adult rats exhibited a tendency to suppression of whole major seizures, whereas specific suppression of the tonic phase was observed in rat pups during the first three weeks of life. The only effect seen in 25-day-old animals was prolongation of the latency of major seizures after the highest dose of progabide.