Osteoporosis is one of the most common skeletal disorders affecting postmenopausal women. The purpose of this study was to investigate whether a 24-week program of aerobic high-impact loading exercise was beneficial for enhancing physical fitness and bone mineral density (BMD) in osteopenic postmenopausal women. Forty-three postmenopausal women aged 48-65 years participated in this study. The BMD of the spine (L2-L4) and right femoral neck of each woman was below 1 SD of the mean of premenopausal women, as examined by dual X-ray absorptiometry. The assignment of subjects into exercise or control group was not randomized but based on each subject's anticipated compliance to the 6-month long exercise program. Twenty-two subjects joined the exercise group and attended the training programs and 21 served as the control group. Exercise programs included treadmill walking at an intensity above 70% of maximal oxygen consumption (VO2max) for 30 minutes, followed by 10 minutes of stepping exercise using a 20-cm-high bench. The program was conducted three times per week for 24 weeks. Physical fitness measurements included testing of flexibility, muscular strength and endurance, body composition, and cardiopulmonary fitness. The results showed that the quadriceps strength, muscular endurance, and VO2max in the exercise group had significant improvements, whereas no improvement was found in any of the physical fitness parameters in the control group. The BMD of the L2-L4 and the femoral neck in the exercise group increased 2.0% (P > 0.05) and 6.8% (P < 0.05) and those in the control group decreased 2.3% (P < 0.05) and 1.5% (P > 0.05), respectively. In conclusion, aerobics combined with high-impact exercise at a moderate intensity was effective in offsetting the decline in BMD in osteopenic postmenopausal women.