Various amino-and guanidino-substituted naphthoates and tetrahydronaphthoates were synthesized and evaluated for inhibitory activities against trypsin, plasmin, kallikrein, thrombin and Cl esterase. Among these compounds, phenyl 4-guanidino-1-naphthoate (IIIj) and phenyl 6-guanidino-1-naphthoate (IIIl) exhibited potent and selective trypsin inhibition (IC₅₀ : 4×10^-7 and 5×10^-8 M, respectively) and phenyl 7-guanidino-1, 2, 3, 4-tetrahydro-1-naphthoate (Vb) and p-ethoxycarbonylphenyl 7-guanidino-1, 2, 3, 4-tetrahydro-1-naphthoate (Vg) had selective inhibitory activities against thrombin (IC₅₀ : 4×10^-5 and 1×10^-5 M, respectively).