Betaine (N,N,N-trimethylglycine) and N,N-dimethylglycine have been reported to have anticonvulsant properties in animals. The purpose of the present study was to determine whether these compounds can antagonize strychnine-induced seizures when administered intraperitoneally and to compare their effects with those of sarcosine (N-methylglycine) and glycine. Betaine, N,N-dimethylglycine and sarcosine were equipotent in decreasing the incidence of seizures and death, causing a 38 to 72 percent decrease in the incidence of seizures and death at a dosage of 5 mmole/kg. Glycine had no effect. Thus anticonvulsant activity is conferred to glycine by a single N-methylation.