The purpose of this study was to investigate the interaction of age and cognitive representations of hypertension in predicting blood pressure. A model of illness self-regulation was used as the theoretical framework for the study. Secondary analysis of data collected from 224 hypertensive adult outpatients was conducted to assess five constructs of illness. ANOVA results indicated that older adults reported fewer hypertension-related symptoms than younger-and middle-aged adults, and that younger adults reported fewer health behaviors to control hypertension than did middle-aged and older adults. Results of hierarchical multiple regression models indicated that after adjusting for effects of demographic factors, no single cognitive representation construct was a significant predictor of blood pressure. The interactions of age and three cognitive representation constructs were, however, significant predictors of blood pressure. For younger adults, increases in the perceived Consequences, Control, and Timeline for hypertension were predictive of decreases in hypertension, although for older adults increased perceptions of control were associated with increased blood pressure.