OBJECTIVE To evaluate the effect of 75 mg oestradiol implants on the bone mass of older postmenopausal women with osteoporosis. METHODS One year prospective-controlled study. METHODS Thirty-two postmenopausal women over 60 years of age and more than five years postmenopausal with low bone density were recruited. Thirty women completed treatment for one year with 75 mg oestradiol implants. The changes in bone density were compared with a control group of 14 women. The side effects with treatment were documented. METHODS Dual energy X-ray absorptiometry of the lumbar spine and proximal femur using Hologic 1000 QDR before treatment and at one year. Plasma oestradiol assays were performed before and after one year. RESULTS The median percentage changes in the treated group after one year was 12.6% at the lumbar spine and 5.22% at the total hip. The increase in vertebral bone density was greatest in women with low initial bone density (r = -0.35, P < 0.05) and those with highest treatment plasma oestradiol levels (r = 0.47, P < 0.01). Side effects were common but most were transient and mild in nature. CONCLUSIONS 75 mg oestradiol implants significantly increase the bone mineral density at the spine and hip of older postmenopausal women with established osteoporosis.