We investigated how cognitive abilities and illness experience relate to illness knowledge. One hundred and forty-eight community-dwelling older adults including hypertensive patients and healthy adults completed a battery that measured illness knowledge, fluid cognitive abilities, crystallized abilities, and health history. Results suggested that hypertension knowledge was primarily associated with illness duration (despite a negative relationship between illness duration and fluid ability) and crystallized ability. Also, greater illness knowledge was associated with an illness perception that may be more consistent with self-care (e.g., greater sense of control). Implications for patient education and training are discussed.