A series of quinazolin-4(3H)-ones and tetrahydrocarbazol-1-ones have been synthesized and their radical scavenging activities have been studied by 1,1-diphenyl-2-picryl-hydrazyl, (DPPH) method. All synthesized compounds exhibited antioxidant property and have been compared with standard antioxidant butylated hydroxy toluene, (BHT). Out of six compounds screened in quinazolinone, 2-thioxo-2,3-dihydro-1H-quinazolin-4-one showed interesting activity as well as in tetrahydrocabazolone series 6-chloro-2,3,4,9-tetrahydro- carbaol-1-one showed good activity.