Objective:To investigate the mechanism of vascular endothelial growth factor(VEGF) expression in osteoblasts induced by durative pressure. Methods:Osteoblasts were isolated from the calvarias of neonatal(12 days old) Sprague-Dawley rats, cultured and identified according to published protocols. The cells were pretreated with or without PD98059 and cultured for 0.5, 2.0, 6.0 h under 100 kpa of pressure in sealed containers. The VEGF concentrations secreted into DMEM were detected by ELLSA. The mRNA levels of VEGF were evaluated by RT-PCR. The total ERK1/2 and the phosphorylation of ERK1/2 in osteoblasts were detected by Western blot. Results:The durative pressure increased the expression and secretion of VEGF, and meanwhile the phosphorylation of ERK1/2 in osteoblasts increased significantly. Pretreated the osteoblasts with PD98059 inhibited the phosphoryation of ERK1/2 and reduced the the expression and secretion of VEGF significantly. Conclusion:Durative pressure induces the expression of VEGF in osteoblasts by the activation of ERK1/2.