Dichlormezanone is the skeletal muscle relaxant. This metathiazanone was found to have a mephenesin-like type of action characterized by paralyzing, anticonvulsant, and hypothermic activities. Dichlormezanone produced an ascending type of paralysis, associated with a marked ataxia. It has anti-electroshock and anti-chemoshock activities. It was found to be active after oral administration and to have a prolonged duration of action. The daily administration of sublethal doses of dichlormezanone to albino rats for 5 consecutive days produced only an initial loss of weight. No significant hematologic alteration or macroscopic lesion of any of the viscera, attributable to medication with either drug, was observed.