Studies focussed on the interactions between masticatory function and the variation in craniofacial height have received an important impulse by the availability of non-invasive imaging techniques like CT and MRI. These techniques allow for in vivo determination of the cross-sectional area and spatial orientation of the human jaw muscles. In recent MRI studies it has been established that the jaw muscles of long-face subjects are up to 30% smaller than those of normal individuals, while the position of the muscles was fairly comparable in both groups. The maximum bite force of long-face subjects is roughly half that of normals. The observed variation of the in vivo data of normal and long-face jaw muscle geometry does explain only half of the difference in their average maximum bite force. The jaw muscles of long-face and normal subjects are presumably different with respect to their force generating capacity per unit of cross-sectional area, which may be attributed to a different muscle fiber type composition.