Ultrasound has been applied therapeutically to accelerate connective tissue healing and healing of long bone fracture. We performed this study to evaluate the effect of therapeutic low energy ultrasound on cultured human articular chondrocyte. Chondrocytes were isolated from articular cartilage of knee joint of young adult during notchy plasty of ACL reconstructive procedure using collagenase and cultured in DMEM solution. Therapeutic ultrasounds ( Intensity ; 1W/cm2, 0.75W/cm2, 0.25W/cm2. Frequency ; 1 MHz) were applied at the cultured human articular cartilage for 0, 30, 60, 90 seconds, repectively. 3H-Thymidine uptake, 3H-Uridine uptake and production of collagen Type I, Type II were evaluated on 3 days, and 5 days of culture. Decreased cell proliferation, decreased thymidine and uridine uptake, decreased production of human collagen Type I and complete loss of production of human collagen Type II were showed after high dose ultrasound application( 1W/cm2, 0.75W/cm2, 1MHz). After low dose ultrasound application( 0.25W/cm2, 1MHz), there were increased cell proliferation and increased production of human collagen Type II and production of Type I collagen was not changed after 3 days and 5 days. In summary, this study showed that decreased cell proliferation and collagen synthesis were observed with application of high dose ultrasound, whereas, increased cell proliferation and human collagen Type II synthesis were observed with application of low dose ultrasound.