A good understanding and knowledge of osteoporosis is a prerequisite for the success of preventive measures as well as treatment adherence. Objective: To assess knowledge about osteoporosis in postmenopausal women with osteoporosis or osteopenia undergoing antiresorptive treatment. Subjects and methods: A cross-sectional study was based on a sample of 232 postmenopausal women with osteopenia or osteoporosis diagnosed by bone density studies and seen at the Menopause Outpatient Clinic at Caism/Unicamp. Women's knowledge of osteoporosis was assessed by means of the OPQ (Osteoporosis questionnaire), a 20-item questionnaire about osteoporosis in areas of general information, risk factors, consequences and treatment. Results: The average age of the women was 61.6 years (+/- 8.2 years) and the average time since menopause was 16.8 years. The average knowledge score obtained by the OPQ was 3.78. The average score for correct answers was 9.8 points, while the average score for incorrect answers was 6 points and 'don't know' answers was 4.1 points. Bivariate analysis showed the variables most closely associated with greater knowledge: education (p < 0.01), reading (p < 0.02), socioeconomic status (p < 0.03), means of acquiring osteoporosis medication (p < 0.02), and absence of comorbidities (p < 0.04). On multiple regression analysis, the factors which remained associated with better knowledge were higher education, higher socioeconomic status scores and absence of comorbidities. Conclusion: Knowledge of osteoporosis in postmenopausal women diagnosed with the disease was limited. Level of education was a strong predictor of knowledge. (C) 2011 Elsevier Ireland Ltd. All rights reserved.6918185