Few studies have compared quantitative ultrasound with bone mineral density (BMD) in monitoring response to therapy in osteoporosis. The aim of our study was to compare finger ultrasound variables and BMD for monitoring alendronate and estradiol therapy in postmenopausal women. We recruited 26 women aged 50 to 79 yr (mean: 65 yr) with osteoporosis; 18 patients received 10 mg/d of alendronate and 500 mg/d of calcium carbonate and 8 patients received 500 mg/d of calcium carbonate only. We recruited 21 hysterectomized postmenopausal women who were randomized to treatment or control. The treatment group received a 25-mg estradiol implant, which was replaced every 6 mo. The control group had a sham procedure. In the alendronate group, there were significant changes at 1 yr at the lumbar spine (p<0.05), bone transmission time (p<0.01), and pure speed of sound (p<0.001) and the changes continued into the second year. In the estradiol implant group, there were significant changes at 1 yr at the lumbar spine (p<0.001), the femoral neck (p<0.05), and the pure speed of sound (p<0.01). For alendronate, the signal-to-noise ratio was similar between the lumbar spine and bone transmission time (1.8 and 1.4) and greater than for the pure speed of sound and femoral neck (0.8 and 0.7); for estradiol, the signal-to-noise ratio was similar between the lumbar spine and femoral neck (2.0 and 1.5) and greater than for the pure speed of sound and bone transmission time (1.1 and 0.6). These results indicated that changes in finger ultrasound are similar in clinical utility to dual-energy X-ray absorptiometry measurements at the femoral neck for the monitoring of antiresorptive treatments for osteoporosis.