N-[N-(4-Deoxy-4-amino-10-methylpteroyl)-4-fluoroglutamyl]-ga mma-glutamate has been synthesized and its ability to serve as a substrate for folylpolyglutamate synthetase and gamma-glutamyl hydrolase has been investigated. It was anticipated that this compound would be a substrate for both of these enzymes. Although the title compound proved to be a good substrate for folylpolyglutamate synthetase, hydrolysis catalyzed by gamma-glutamyl hydrolase was unexpectedly slow. These results suggest the use of fluoroglutamate-containing peptides as hydrolase-resistant folates or antifols in a variety of chemotherapeutic regimens.