Substrates containing the fluorescent reporter group 6-amino-1-naphthalene-sulfonamide (ANSN) are useful compounds for monitoring the enzyme activity of various serine proteases (1-12). In this class of compounds, the ANSN reporter group is linked (in the R1 position) to short tri-peptide sequences. The peptide sequences are designed to optimize the interaction between the enzyme and substrate. Additional components which may be added to the R2 and R3 positions reflect changes in the P' subsite positions, and generally affect the kinetic parameters of the substrates. Compounds which are effective substrates are hydrolyzed between the tri-peptide and the ANSN group. Once cleaved from the peptide moiety, the ANSN group exhibits about a 1000 fold increase in relative fluorescence.