A review of relevant literature was undertaken because of concerns about a possible relationship between pet foods, development of periodontal disease, and secondary adverse effects on general health. It was concluded that, while changes in feeding methods in recent decades have arguably improved pet health by reducing or preventing diseases associated with nutritional deficiencies and excesses, periodontal disease remains a serious, diet-related problem. There is reasonable evidence that soft diets are associated with increased frequency and severity of periodontal disease, and that harder foods requiring vigorous prehension and mastication are preferable for dogs and cats. While it is plausible that periodontal disease could cause diseases in other organs and tissues, the evidence for this is limited at present. Further research is needed to better define the relationship between diet types and oral health. In the meantime, veterinarians and pet owners should pay attention to the physical qualities (textures, abrasiveness, 'chewiness') of foods they provide for dogs and cats, as well as to their nutrient content, and should consider additional methods to control plaque and prevent periodontal disease where necessary.