The principles of managed care are more difficult to apply to preventi
ve medical treatments, such as hormone replacement therapy, than to th
e investigation and treatment of established disease. In addition to a
n ageing society with increased health demands, the use of hormone rep
lacement therapy is increasing in most developed countries. Clinical g
uidelines for the counselling of post-menopausal women and the use of
hormone replacement therapy have been prepared by the American College
of Physicians. There is limited information about the benefits and ri
sks of hormone replacement therapy from randomized prospective studies
and these guidelines are based on the best available data from observ
ational studies and meta-analysis. More secure data will become availa
ble within the next decade from long-term studies that are currently i
n progress. Managed care proposals for hormone replacement therapy mus
t be flexible enough to adjust to new data as they become available wh
ile recognizing that, given current knowledge, hormone replacement is
healthcare-cost-effective for the vast majority of menopausal women.