[en] A potent chemotactic peptide, formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-lysine was derivatized by reaction with N-succinimidyl 4-fluorobenzoate. This derivatized peptide bound to human polymorphonuclear leukocytes in vitro and exhibited biological activity in a superoxide production assay. Peptide labeling using N-succinimidyl 4-[¹⁸F]fluorobenzoate was accomplished in reasonable yields with 10-15 mCi of labeled peptide available per 100 Ci of [¹⁸F]fluoride. With the exception of the gastrointestinal tract, clearance of activity from tissues following injection of this peptide in normal mice was rapid. Although preliminary in nature, these results suggest that ¹⁸F-labeled chemotactic peptides should be investigated as potential agents for positron emission tomographic imaging of bacterial infections