Background: Root caries is considered a serious problem affecting the long term prognosis of both treated and untreated periodontally involved teeth and have become a major public health problem among adults. Aim: To assess root caries risk among subjects with periodontal disease using the Cariogram study model. Methodology: A descriptive cross-sectional study was conducted among 220 participants aged ≥ 35years who were categorized as cases and controls based on inclusion criteria. Data was collected using the specially designed proforma. Clinical oral examination was done for recording plaque scores (Silness and Loe), periodontal status and dental caries experience (WHO 1997). Salivary profile was generated by recording stimulated salivary flow rate, buffering capacity and microbiological status. Results: Cariogram model revealed 39% and 51 % chance of avoiding caries for cases and controls respectively. Higher coronal and root caries experience was observed among cases than controls. Subjects categorized into high risk, according to cardiogram had higher mean DMFT (16.79 ± 4.58) and RDFT (1.47 ± 1.27) than other risk groups. Active periodontal disease and past caries experience were significantly associated with root caries through logistic regression analysis. Conclusion: Cariogram can be a useful tool to illustrate caries risk profiles among periodontal disease patients. Along with baseline root caries experience, active periodontal disease, plaque, lactobacilli and mutans streptococci were identified as a major risk factors associated with root caries.