To investigate the involvement of apoptosis and proliferation in the lesions of hypertrophic scars and keloids, eighteen samples of hypertrophic scar and five samples of keloid were collected. The apoptosis was detected with terminal deoxynucleatidyl transferase mediated d-UTP biotin nick end labeling(TUNEL) and the expression of PCNA was assessed with immunohistochemical technique in scar lesions and normal skin. Results showed that in hypertrophic scar and keloid samples the rate of proliferating cells in dermis was higher than that of normal skin(P < 0.05), whereas the apoptosis index between scars and normal skin shows no statistical significance. It indicates that excessive proliferation and the lack of apoptosis of cells in dermis may cause the formation and development of hypertrophic scars and keloids.