Eight l-aryl-3{2-pyridyl)thiobarbiturates were synthesized and evaluated for their anticonvulsant property and their ability to inhibit succinate dehydrogenase activity of rat brain homogenates. These substituted thiobarbiturates (100 mg./kg., i.p.) provided 20-60% protection against pentylenetetrazol-induced convulsions in albino mice. Low toxicity of these compounds was reflected by their high approximate LD,, values which were found to range from 500-1000 mg./kg. All substituted thiobarbiturates (1mM) inhibited in uitro succinate dehydrogenase activity and the degree of inhibition ranged from 10-72%.