A new series of inhibitors was designed based on the naphthalene ring system in an effort to shift the absorption maximum of these inhibitors to longer wavelength (Fig. 2). The naphthalene ring system is substituted in different positions with a hydroxyl group, a cinnamate ester, and an electron-donating group. In this presentation inhibitors for chymotrypsin, thrombin, and factor Xa will be introduced and their inhibition efficiencies will be discussed.