Both tibolone and raloxifene have been demonstrated to prevent postmenopausal bone loss. During treatment with tibolone bone mineral density (BMD) of the spine has been shown to be increased between 1.8 and 5.8 % above baseline in two years, depending on the population studied. Since treatments aimed at prevention should ideally be used long-term, compliance with the treatment is crucial. Efficacy of and compliance with the two treatments will be measured and evaluated.