Growth and development of maxillofacial morphology and oral function are closely interrelated. Oral function is comprised of articulation, swallowing, and chewing. Malocclusion may be caused by abnormal functions such as mouth breathing, tongue thrust swallowing, and unilateral chewing and by abnormal postures of oral circumferential muscles such as forward tongue thrust, tongue biting, and low tongue at rest. Forces from unintentional and habitual behaviors constantly acting on the maxillofacial and alveolar regions can cause the bony structures to generally deform, resulting in jaw deformity and malocclusion. Oral function also plays a vital role in maintaining body posture. In this study, clinical observations of oral postures examined maxillary protrusion and open bite, anterior crossbite and facial asymmetry. The unstable forces induced by abnormal posture were correlated with the varieties of malocclusion. Morphology, function, and posture were shown to be closely interrelated and to influence each other.