Backgrounds: Osteoporosis is largely preventable and the main principle in the prevention is knowing the people's belief, lifestyle and daily habits. This study was performed to determine the knowledge, belief and practice of elderly about osteoporosis based on Health Belief Model in Karaj city, Iran.

Methods: This descriptive-analytical survey  in 2014 was conducted on 286 elderly of Karaj city (Iran) by cluster random sampling method. For data collection the questionnaire included demographic information, knowledge, beliefs (based on Health Belief Model) and practice was used. Data were analyzed by SPSS and  ANOVA, Chi-square, T-test, Pearson correlation and Regression tests.    

Results: In this study 65/4% of elderly had no knowledge about osteoporosis and only 22/5 % had  positive belief about the prevention of it. Most of participants had undesirable behavior. Between level of awareness with daily calcium intake and physical activity was a significant relationship (P<0/05). perceived benefits were identified  as the most significant predictors of behavior.  

Conclusion: According to the results, it seems that should pay more attention to raise awareness, modify the belief and behavior of elderly about prevention of osteoporosis. So it is suggested that instructional programs using behavioral science theories, and instructional methods and media be designed to improve the present situation.