Eight 4-aryl-1-(2,3,4-trihydroxy acetophenone)-3-thiosemicarbazones were synthesised and evaluated for their ability to inhibit rat brain monoamine oxidase (MAO). All compounds exhibited concentration dependent inhibition of enzyme. The degree of enzyme inhibition was also evaluated on the basis of their I50 and I50/(S) values. Preincubation of these compounds with the enzyme system for varying lengths of time prior to the addition of substrate in no way altered their degree of inhibition. Kinetic study carried out with 4-(2-methoxyphenyl)-1-(2,3,4-trihydroxyacetophenone)-3-thiosemicarbazone revealed a competitive nature of inhibition. Anticonvulsant activity exhibited by these thiosemicarbazones (100mg/kg, i.p.) against pentylene-tetrazol-induced seizures ranged between 10-60%. Low toxicity possessed by these compounds was reflected by their approximate LD50 values ranging from 750 mg/kg to greater than 1000 mg/kg.