Key messages * Osteoporosis is a disease characterised by low bone mineral density, 80% of which is under genetic control * Vitamin D has an important role in the metabolism of calcium and bone, mediated through its receptor * Common variants of the vitamin D receptor gene are responsible for 7-10% of the difference in bone density between women after the menopause * This genetic marker is important because of its potential role in identifying individual women at increased risk of fracture before menopause and in selecting optimal treatment selecting optimal treatment based on the understanding of pathophysiological mechanisms. Because of discrepancies between population groups, further studies are needed, with larger sample sizes that include a range of ages in both men and women. The demonstration of the effect of these common vitamin D receptor genotypes on bone mineral density in a second, geographically distinct population of older and postmenopausal women opens the way to a wide range of studies to provide novel approaches to the prevention and treatment of osteoporosis. Design-Open controlled trial in patients admitted consecutively and randomised to treatment with either oral co-amoxiclav, intravenous followed by oral co-amoxiclav, or intravenous followed by oral cephalosporins.Setting-Large general hospital in Dublin. Patients-541 patients admitted for lower respiratory tract infection during one year. Patients represented 87% of admissions with the diagnosis and excluded those who were immunocompromised and patients with severe life threatening infection.Main outcome measures-Cure, partial cure, extended antibiotic treatment, change of antibiotic, death, and cost and duration ofhospital stay.