Ten areas of health knowledge were investigated in 2 studies, 1 of college students (N = 169) and 1 of adults from the community (ages 19-70; N = 176). Measures assessed knowledge of aging, orthopedic/dermatological concerns, common illnesses, childhood/early life, serious illnesses, mental health, nutrition, reproduction, safety, and treatment of illness/disease. Significant gender differences favoring women were found for most areas of health knowledge, especially reproduction and early life. Results showed that cognitive ability accounted for the most variance in health knowledge with nonability (personality and interest traits) and demographic variables accounting for smaller but significant amounts of variance across most knowledge domains.