Introduction and Hypothesis: Lymphatic vasculature exquisitely controls the clearance of metabolic end products, removal of bacterial endotoxins, and trafficking of immune cells. Signaling pathways that converge into endothelial cell kruppel-like factor 4 (KLF4) provide an atheroprotective role; however, the role of lymphatic endothelial cell (LEC)-KLF4 in these processes has not been clarified. Thus, we examined whether LEC-specific deletion of Klf4 alleles LECs. Methods and Results: After several generations of breeding, we transferred ROSA mT/mG (dual-fluorescent reporter allele mT/mG) to Prox1 CreERT2 (tamoxifen, TAM) inducible mice in C57 background to generate ROSA mT/mG ::Prox1 CreERT2 mice. In the next breeding scheme, ROSA mT/mG ::Prox1 CreERT2 female mice were crossed with male Klf4 fl/wt (Klf4 floxed allele) mice to generate heterozygous ROSA mT/mG ::Prox1 CreERT2 ::Klf4 fl/wt offspring (50%). Thereafter, we bred male ROSA mT/mG ::Prox1 CreERT2 ::Klf4 fl/wt with female ROSA mT/mG ::Prox1 CreERT2 ::Klf4 fl/wt to produce ROSA mT/mG ::Prox1 CreERT2 ::Klf4 fl/fl genotype (25%). These mice (12-14 weeks old) received TAM for five consecutive days, and on 21 st or 28 th day all mice were sacrificed. To confirm LEC Cre activation after TAM administration, we prepared cryosections of lung and the heart tissues. Mice receiving TAM showed lively and clear separation of green fluorescent protein (GFP) and tomato-Red colors, showing LEC specificity of Prox1 CreERT2 transgenic methodology. Cryosectioning combined with low- and high-resolution microscopy, and morphometric analyses of H&E sections showed disruption of LEC function and integrity in these mice. Biochemical experiments underway will address the role of KLF4 in lymphatic vessels homeostasis. Conclusion: These results indicate a key role for Klf4 in the regulation of lymphatic vessels.