[en] OBJECTIVE: Our purpose was to review with critical analysis, data from randomized controlled clinical trials comparing the effects on bone of conventional hormone replacement therapy (HRT) and tibolone. Their respective effects on bone were also reviewed and summarized. Materials and methods. Medline via PubMed was searched using a combination of the following key words "tibolone, estrogens and bone" to identify all randomized controlled trials tibolone versus HRT (1960-2001). RESULTS: Six randomized controlled trials that have been carried out to compare effects of tibolone and conventional HRT on prevention of postmenopausal bone loss were identified. Only one of these trials has been performed with a correct methodology (double-blind and with an adequate duration). In this trial over 2 years, the highest significant increase from baseline in bone mineral density (BMD) at all sites was observed with HRT; in addition, HRT showed a significantly greater increase in BMD at lumbar spine than tibolone. Randomized placebo-controlled trials have demonstrated that tibolone produces positive effects on BMD. Nevertheless, no clinical convincing data are available to support its efficacy in the prevention of osteoporotic fractures. The positive impact on BMD of conventional HRT to prevent postmenopausal bone loss and to treat established osteoporosis has been shown by many randomized controlled trials. Regarding fracture risk prevention, some clinical and epidemiological data suggest that HRT initiated in early or late postmenopause may prevent fractures if it is administered at standard doses and continued for a long time. CONCLUSION: HRT is always the reference treatment of postmenopausal symptoms related to estrogen deficiency.