These structures were investigated with various histological stains and by polarization microscopy. The width of the periosteal layers was measured in nine ramal and condylar areas at five different ages (0, 2, 6, 12 and 30 weeks). The total periosteal width changed during growth, as did the absolute and relative thickness of its cellular and fibrous layers. The results suggest that in these areas periosteal tension may influence growth of the condylar cartilage, and that this may vary during growth.