The anticonvulsant activity of a salt of valproic acid (VA), magnesium valproate (MgV), was assessed against amygdala-kindled seizures in rats. The anti-epileptic power of MgV was compared with that of sodium valproate (NaV). Kindling was obtained by delivering daily to one of the amygdala a 2 s train of monophasic square-wave pulses (1 ms, 60 c.p.s., 100-130 microA) via chronically implanted electrodes. Magnesium valproate and NaV were tested once kindling was stabilized and the post-kindling threshold for generalized convulsions was determined. The drugs were administered intraperitoneally in doses ranging from 25 to 200 mg/kg. The injection/test interval was 30 min. Each animal received a single dose every 24 h. Magnesium valproate exhibited an anticonvulsant activity qualitatively and quantitatively similar to that of NaV. Statistically significant differences were not found between the two drugs with respect to the reduction of seizure severity and afterdischarge (AD) duration. The calculated ED50's were 94.58 and 97.41 mg/kg for the suppression of generalized seizures, 176.96 and 129.26 mg/kg for the suppression of partial seizures, 275.96 and 224.13 mg/kg for the suppression of the local AD in the MgV and NaV treated groups, respectively.