Lipopolysaccharide (LPS) evokes human pulmonary microvascular endothelial cell hyperpermeability. The paracellular permeability of human pulmonary microvascular endothelial cells was measured at different LPS dosages and at different time points after LPS intervention. The results showed that paracellular permeability had no significant alterations after LPS addition with dosages below 10 ng/mL. However, the paracellular permeability significantly increased after LPS stimulation with dosages above 100 ng/mL in a dose-dependent manner (A). Furthermore, we observed that paracellular permeability significantly increased after 6 hours following 100 ng/mL LPS addition in a time-dependent manner (B). Shown are the mean ± standard error of three parallel experiments (n = 3, **P <0.01 versus group 0 ng/mL or 0 hours).