Novel 4-(4-bromophenyl)phthalazine and phthalazinone derivatives connected through 2-propanol spacer to N-substituted piperazine residue were synthesized. All the new compounds were screened for their effect on b-adrenergic blocking activity on the norepinephrine-induced precontracted aortic ring module. Most test compounds displayed appreciable b-adrenolytic activity compared to propranolol as a reference standard. The results have shown that compounds 3a, 3d, 3e and 7c displayed appreciable inhibition of norepinephrineinduced aortic ring contraction.