Expression of E- and P-selectin ligands is required for T cell entry into skin. Sialyl Lewis X moieties are critical for ligand activity and are elevated on malignant skin-homing T cells. We hypothesize that these glycosylations are selectable targets for treating the dermal tropism associated with cutaneous lymphomas. In this study, we analyzed the efficacy of a novel 4-fluorinated analog of N-acetylglucosamine (GlcNAc) on E- and P-selectin ligands expressed by malignant skin-homing T cells. We also examined the specificity of 4-F-GlcNAc (2-acetamido-1,3,6-tri-O-acetyl-4-deoxy-4-fluoro-D-glucopyranose) action by contrasting the effects on sialyl Lewis X expression displayed by P-selectin glycoprotein ligand-1 (PSGL-1) with sialylated O-glycans expressed by CD43. Using parallel-plate flow analysis, we found that 4-F-GlcNAc elicited 5-fold more potent inhibition on P-selectin ligand activity than on E-selectin ligand activity. To determine whether glycosylations conferring E- and P-selectin ligand activities were inhibited, we analyzed the expression of sialyl Lewis X and sialyl-fucosylated core 2 O-glycan (CHO-131 antigen), respectively. We found that 4-F-GlcNAc treatment resulted in dose-dependent ablation of sialyl Lewis X and CHO-131 antigen expression on PSGL-1, whereas sialylated O-glycans on CD43 were minimally affected. These results indicate that 4-F-GlcNAc treatment can selectively downregulate the P-selectin ligand activity and potentially prevent dermal dissemination of cutaneous lymphomas.