Both Alzheimer's disease and osteoporosis occur mainly in persons aged over 60. Both diseases are often seen to co-occur in clinical practice, yet very few investigators have addressed this problem. They have demonstrated that several different clinical factors can lead to a higher incidence of osteoporosis in persons with Alzheimer's disease. Serum concentrations of vitamins D and K, calcium and PTH; the duration of sunlight exposure; dietary calcium intake; genetic factors as well as the effect of oestrogens on mineral bone density in patients with and without dementia have been studied. Furthermore, the effects of vitamin D and calcium preparations with or without bisphosphonates (risedronate) have also been assessed. The authors concertedly emphasise that the treatment of patients with dementia needs to include the prophylaxis of osteoporosis, falls and fractures.