Background: Asymmetric dimethylarginine (ADMA) induces endothelial cell barrier dysfunction via cytoskeleton activation and contraction. It is supposed that activated p38 mitogen-activated protein kinase (MAPK) would trigger the formation of stress fibers and increase cellular permeability. Objective: Explore p38 MAPK as a potentially important enzyme in ADMA-mediated endothelial cell contractile response and permeability change. Methods: Human umbilical endothelial cells (HUVECs) were cultured, where ADMA and/or SB203580 (the specific inhibitor of p38MAPK) were used to stimulate HUVECs. Immunofluorescent staining was carried out to examine the expression and distribution of F-actin, flow cytometry was used to quantify F-actin, and Transwell was applied to test cellular permeability with FITC-labelled human serum albumin (HSA). Scanning electronic microscopy (SEM) was utilized to observe the changes of intercellar contact. Results: ADMA induced significant p38MAPK activation in a dose-dependent manner, which correlated with increased stress fibers. SB-203580 attenuated the formation of actin stress fiber and the increase of cellular permeability induced ADMA in the HUVECs (p<0.01, LSCM; p<0.01, cytometry; p<0.05, Transwell). Widened intercellular space induced by ADMA was detected and could be inhibited by SB-203580 (SEM). SB-203580 alone had no effect on cytoskeleton and cellular permeability. Conclusion: p38MAPK activation participated in cytoskeleton and cellular permeability changes induced by ADMA in HUVECs.