A new series of 1-(1, 3-benzodioxol-5-ylmethyl)-3-[4-(1H-Imidazol-1-yl) phenoxy]-piperidine analogs were designed and identified as potent and selective inhibitors of NO formation based both on the crystal structure of a murine iNOS Δ114 monomer domain/inhibitor complex and inhibition of the NO formation in human A172 cell assays. Compound 12S showed high potency and high iNOS selectivity versus nNOS and eNOS.