BACKGROUND More than half of those with chronic diseases, including osteoporosis, discontinue treatment during the first year of its administration. This problem increases over the course of continued follow-up. Additionally, it has been observed that 13% of women, prescribed oral daily alendronate, do not even start the treatment, while 20% of patients discontinue the therapy during the first four months. On the other hand, those patients who are compliant achieve increased bone mass density with a simultaneous decrease of fracture risk. The aim of our study was to assess the adherence to the recommended alendronate 70 administration protocol over the course of 12 months by women with post-menopausal osteoporosis. METHODS Adherence (compliance plus persistence) to alendronate 70 therapy was assessed in a prospective study of 153 post-menopausal women, followed up for one year with monitoring every two months. RESULTS Adherence to therapy of all the study participants was high during the entire study period, the patients remaining compliant after a year in 95.08 ± 1.39% (mean ± SEM) of cases, and the mean persistence with medication was 347.05 ± 5.07 days. In the group of patients who interrupted treatment, the mean persistence was 212.44 days. One of the study participants did not start the treatment, and another two discontinued the therapy within 30-60 days of the study onset (between the first two visits). Facilitated contacts with the doctor, continuous access to prescribed treatment and frequent visits significantly improved patient compliance. The common reason for discontinuation was side effects, while age (but not education) affected the rate of compliance with therapy. The worst results were obtained in the group of patients with osteoporosis diagnosed more than five years before the study, particularly in the subgroup where alendronate was being used for the first time or where treatment resumed after a substantial break. CONCLUSIONS The obtained results indicate that better adherence to alendronate 70 therapy, administered once a week, depends on more frequent monitoring of treated patients.