A series of analogues of 2-iminopiperidine have been prepared and shown to be potent inhibitors of the human nitric oxide synthase (NOS) isoforms. Methyl substitutions on the 4- position (3) or 4-and 6-positions (8) afforded the most potent analogues. These compounds exibited IC50 values of 0.1 and 0.08 μM, respectively, for hiNOS inhibition. Substitution with cyclohexylmethyl at the 6-position (13) afforded an inhibitor that showed the best ...