Recently, people start to pay attention to the effects of physical factors on cell differentiation and function. In this review, we introduce the effect of mechanical stress on chondrocytes for engineerd cartilage by "Tissue engineering" . To reconstruct articular cartilage, it is important to re-differentiate chondrocytes that have de-differentiated along with cell proliferation in vitro . We show here hydrostatic pressure that is a mechanical stress applying articular cartilage, promotes re-differentiation of de-differentited chondrocytes by increasing expression of aggrecan and type II collagen. Increasing evidence suggests that mechanical stress, as well as other factors, may significantly increase the biosynthetic activity of cells in bioartificial matrices. Incorporating effects of mechanical stress on cellular phenotype should result in safer and more efficacious repairs and replacements for the surgeons and patients.