Even if the preventive programmes against dental disease in place today were to be highly successful there would still be individuals developing large numbers of carious lesions. It is therefore important to find methods to detect early those individuals who are prone to develop caries and then to institute special preventive programmes for them. The importance of such systems will increase when the general level of dental health improves. Then the high-caries group will require a proportionally larger part of the total dental care provided. The number of false-positive decisions will increase as the proportion of high caries risk individuals decreases. To a certain extent, this will mean that the application of specifically designed and expensive preventive programmes for predicted high-risk individuals will result in a low cost-effectiveness ratio. In a clinical study the possibility of predicting high caries risk pre-school children was analysed.