AIM. The Biphosphonates Efficacy-Safety Tradeoff (BEST) study was designed to evaluate efficacy and safety of oral BP in primary care. METHODS. Hospital discharges and pharmacy claims, collected over a population of 19 million enrolees in the Italian National Health System, were used to select records of subjects aged 55+ years, discharged from hospital with a primary diagnosis of fracture at osteoporotic sites. Exclusion criteria included cancer, Paget disease, and previous BP use. Post-discharge prescription of oral BP was recorded. Outcomes of the BEST study are: 1) occurrence of osteonecrosis of the jaw (ONJ), 2) gastro-intestinal bleeding, and 3) recurrent fracture. Data on BP utilization and ICD9CM-based diagnoses of ONJ are currently available. RESULTS. Out of 72,675 eligible subjects (mean age: 67 years; 71% females), 11% (females: 16%, males: 6%; p<0.001) received at least one BP prescription in the follow-up. Peak prescription rate (26% in females and 19% in males) was reached at age 70-74 years and declined sharply thereafter, being below 7% after the age of 85 in both sexes (age trend: p<0.001). Based upon selected ICD9CM codes, 135 cases of possible and 162 of probable ONJ were identified; the corresponding incidence densities were 0.15 and 0.22 per 10,000 person-years, respectively. Association with BF use will be evaluated after adjudication of final diagnoses by an expert panel. CONCLUSIONS. In this large sample of Italian population with such a compelling indication as an osteoporotic fracture, BP are substantially underprescribed, especially in oldest subjects.