A series of new 7-acyl substituted 1-benzoxepanes and 5-acyl substituted 2-methyl-1-benzoxolanes were synthesized and studied for anti-inflammatory properties. The benzoyl derivatives were more active than the corresponding halogenobenzoyl derivatives and previously reported structural analogues containing less methylene groups in their heterocyclic ring. The introduction of a methyl group at the 2-position of 5-cinnamoyl-1-benzoxolane heterocyclic ring significantly potentiated the activity. Anti-inflammatory and analgesic effects of 7-benzoyl-1-benzoxepane and 5-cinnamoyl-2-methyl-I-benzoxolane were less pronounced than those of indomethacin and diclofenac but greater than those of acetylsalicylic acid (ASA). Both compounds were less toxic and 5-cinnamoyl-2-methyl-1-benzoxolane was also less gastrotoxic than all the reference drugs mentioned above. Therapeutic indices of 5-cinnamoyl-2-methyl-1-benzoxolane were greater than those of diclofenac and significantly greater than those of ASA and indomethacin.