The formation of the cartilage in mandible of human fetuses, which ranged from 12 to 32 weeks gestation, was systematically investigated with immunohistochemystry linked to an image color analyzer. One of the extracellular matrix proteins (type II collagen) was found mainly in the hypertrophic layer of the condyle from 16 weeks gestation. The percentage of type II collagen per 10,000μm2 area using a computer system with an image color analyzer gradually increased from 16 weeks gestation. This analyzer system revealed the value of cell activity by using immunoperoxidase staining. These results suggested that type II collagen effects the formation of mandibular condyle and the temporomandibular joint during embryonic stages.