Clinical experience with cyclical etidronate for the treatment of osteoporosis was reviewed in 69 consecutive patients. Six patients stopped treatment either due to adverse effects (5) or the decision to take hormone replacement therapy (HRT) (1). Bone mineral density (BMD) measurements using dual energy X-ray absorptiometry (DXA) were obtained in 63 patients (33 with spinal osteoporotic fractures and 30 with osteopenia) before and 1 year after treatment. BMD increased by an average of 4.50% (p < 0.001) in the lumbar spine (range +14% to -12%) and 5.5% (p < 0.01) at Ward's triangle (range +31% to -13%) while there was no significant change at the femoral neck (range +11% to -12%) and greater trochanter (range +12% to -15%). Significant rises in BMD were found at the lumbar spine and Ward's triangle in both osteoporotic and osteopenic groups. Of patients analysed after 1 year, 83% had an increased bone mass at the lumbar spine and 55% at the femoral neck. We conclude that there is a wide variation in the bone mass response to cyclical etidronate therapy, and in a minority of patients bone mass does not increase. For the majority of osteoporotic patients, however, we confirm the efficacy and tolerability of cyclical etidronate for the preservation of bone mass over 1 year in a clinical setting.