The primary function of the immune system in the oral cavity is to protect the various structural components such as teeth, jaws, gingivae and oral mucosa against various infections. These host defences mechanism vary in the different oral domains represented by the oral mucosa, saliva and gingival crevice. Cellular and humoral mediated immunity play a major role in immune mediated diseases of oral cavity. Therapeutic agents should only be selected after the thorough evaluation of immune status and once the confirmatory diagnosis has been made. This overview aims to highlight the current state of knowledge of the immune components in each oral domain as it is relevant to the oral cavity in health and disease; also attempt to illustrate the importance of immunology in relevance to the practice of dentistry.