The shear-force value, the total amount of collagen, heat-solubility of collagen and thickness of the perimysium were measured on six kinds of chicken skeletal muscle. Toughness of the meat was significantly correlated with both total amount of collagen (r2=0.94) and thickness of the perimysium (r2=0.95). Although differences in heat-solubility of collagen were observed among the six muscles, heat-solubility of collagen was not correlated to the shearforce value. These results suggest that the total amount of collagen and structures of the perimysium are the major factors determining toughness of chicken.