||The use of effective preventive methods has produced good results in developed countries, where caries is declining and periodontal disease is probably getting no worse. There are special problems with prevention in developing countries, principally high periodontal disease prevalence, rising caries rates and lack of resources to deal with these problems. With appropriate assistance, much can still be accomplished in these developing countries. Depending on economic resources and disease patterns, the following procedures for oral disease prevention can be recommended. Priority order will vary from country to country, and national and local laws may also determine what procedures can or cannot be employed. Fluoridation of water supplies is the most effective action to prevent caries in communities where piped water supplies are in place. It is relatively cheap and does not depend on individual action. Where water fluoridation is not feasible, community-based alternatives are salt fluoridation, school-water fluoridation or supervised ingestion of fluoride supplements. Supervised mouthrinsing with fluoride solutions, usually in schools, is effective in fluoridated and non-fluoridated communities. Dentists or auxiliaries can also apply fluoride gels or solutions to the teeth of individual patients. The use of fluoride toothpastes is recommended wherever possible as a routine part of self care. All preventive activities have an educational component. Community leaders and others should be educated regarding the institution and maintenance of community preventive measures which affect them. Individual patients should be educated regarding their oral hygiene, use of fluoride, restriction of sugary snacks between meals and the necessity for regular dental visits when services are available. Dental health education of the public can be concentrated in special target groups such as expectant mothers. Because dental caries is a public health problem in many countries, public policy to control the availability of highly cariogenic foods should be considered. Fissure sealants, when applied properly, are highly effective in preventing caries in occlusal surfaces. Their use is recommended on newly erupted teeth in susceptible persons, and they may be specially useful in the handicapped. Trained operators are required and the procedure is reasonably expensive; these factors may restrict the use of sealants where resources are limited. The ability of the individual patient to control plaque by toothbrushing, flossing or chewsticks should be developed to the utmost as the first step in controlling periodontal disease. 2+.