New twenty compounds bearing thiazole ring (3a-3t) were designed and synthesized as monoamine oxidase (MAO) inhibitors. The fluorometric enzyme inhibition assay was used to determine the biological effects of synthesized compounds. Most of them showed remarkable inhibitory activity against both MAO-A and MAO-B. By comparing their IC50 values, it can be seen that active derivatives displayed generally selectivity on MAO-B enzyme. Compounds 3j and 3t, which bear dihydroxy moiety at the 3rd and 4th position of phenyl ring, were the most active derivatives in the series against both isoenzymes. Compounds 3j and 3t showed significant inhibition profile on MAO-A with the IC50, values of 0.134 +/- 0.004 mu M and 0.123 +/- 0.005 mu M, respectively, while they performed selectivity against MAO-B with the IC50, values of 0.027 +/- 0.001 mu M and 0.025 +/- 0.001 mu M, respectively. Also, docking studies about these compounds were carried out to evaluate their binding modes on the active regions of MAO-A and MAO-B.