A range of chemical compounds, mostly with central nervous system depressant activity, have been tested against experimental tetanus in the rabbit. A number of the more potent tested, including mephenesin, betanaphthoxyethanol, barbiturates and phenothiazine derivatives, have been accurately assayed by a method of quantitative electromyography. Phenothiazine derivatives were found to be the most potent anticonvulsants and of these acetylpromazine had the greatest activity. The difficulties of direct comparison of the potency of substances from different chemical groups is discussed.