The last two decades have witnessed numerous advances in the treatment of chronic diseases, most notably those occurring in postmenopausal women. An insidious course and minimal symptoms often characterize chronic diseases, with the result that long-term adherence to prescribed treatment regimens may be difficult to obtain. Poor compliance has been abundantly documented, particularly in patients with hypercholesterolemia, hypertension, or diabetes mellitus. Many factors may contribute to poor compliance, including the unobtrusiveness of the symptoms, limited patient awareness of the potential severity of the disease and of the benefits expected from optimal treatment, low level of education, fear of adverse effects from medications, and cost of medications. The effects of these factors vary across countries, in particular according to the characteristics of healthcare systems. Several strategies are being developed to measure compliance and to identify reasons for non-compliance. Attention is turning to methods for improving compliance, some of which rest on general principles and others on the specific characteristics of each disease. Few data are available on compliance with treatments for osteoporosis, since these were introduced only within the last decade. In many studies, the reference standard was hormone replacement therapy (HRT), whose use is decreasing markedly as a result of recent data on adverse effects. Available studies of bisphosphonate therapy indicate a less than 50% continuation rate after 1 year. The few comparative studies published to date have methodological flaws that preclude definitive conclusions. Compliance has been equally poor with all available bisphosphonates. Although statistically significant, the improvements produced by weekly dosing have been modest, about 10%, indicating a need for further compliance-enhancing strategies. Conflicting results were obtained from the few studies addressing the potential of bone turnover marker assays for influencing compliance. Having a nurse inform patients about the disease and the importance of compliance with dosing recommendations holds promise for improving compliance.