Osteoporosis has become a major public health problem. Because the biggest culprit in the process of bone loss is oestrogen deficiency, hormone replacement therapy remains the mainstay for prevention, but prophylaxis by this means is limited. Phyto-oestrogens deserve special mention because emerging data support the suggestion that these weakly oestrogenic compounds, present in plants, may prevent bone loss associated with the menopause and thus represent a potential alternative therapy for a range of hormone-dependent conditions, including postmenopausal symptoms. A substantial body of work in animal models in the past few years has provided convincing data for significant improvements in bone mass and other endpoints following feeding with soya. Thus, phyto-oestrogens appear to have potential promise for maintaining or modestly improving bone mass of human subjects when consumed at optimal dosages. However, we must appreciate the limits of the information reached before extrapolating to man and we need to gather more data before health professionals can actively advocate the increased consumption of soya. Indeed, it will be important further to characterise the physiological effects of phyto-oestrogens and their margins of safety.