Objective: Although caries risk assessment (CRA) and periodontal risk assessment (PRA) are becoming more common methods for focusing the delivery of preventive and clinical services, little has been done to examine the relationship between these two classifications. The objective of this evaluation was to determine whether an association exists between caries and periodontal risk levels. Methods: Using administrative data from a large dental group practice we examined the relationship between CRA and PRA classifications, two independently coded scores, among 14,859 adults. Both trichotomous classifications were collapsed into dichotomous “low” versus “elevated” risk categories. Results: While 40% of the subjects were at elevated caries risk and 44% were at elevated periodontal risk, only 24% categorized at elevated risk for both diseases. A further 40% were at low risk for both diseases Those categorized as being at elevated risk for caries were approximately 2.7 times as likely to have a moderate or high periodontal risk score (p<.001), after controlling for prior caries activity and age. Conclusions: We found an association between caries risk and periodontal risk but we do not know at the present stage of research whether one type of risk assessment (CRA or PRA) is factored in when dentists are evaluating the other type. The nature of the association is probably related to common risk factors, and/or the presence of exposed root surfaces. This project was supported by grant RO1 HS 013339 from AHRQ.