We investigated 2-year longitudinal changes of bone mineral density (BMD) in lumbar spine and proximal femur in 64 Japanese women aged 38-67. Forty subjects were premenopausal (mean age 44.9) and 24 postmenopausal (mean age 54.6) at enrollment of the study. Six subjects experienced menopause during the 2-year study period and were defined as the perimenopausal group. Measurements of BMD were performed using dual-energy X-ray absorptiometry at L2-4, femoral neck, greater trochanter, and Ward's triangle. Paired t test revealed no significant decrease in BMD at any site in the premenopausal group. Significant annual decrease in BMD was observed in the perimenopausal group at L2-4, femoral neck, and greater trochanter. A similar tendency was observed in Ward's triangle, but did not reach statistical significance. In the postmenopausal group, significant decrease in BMD was found at the proximal femur, but not at L2-4. Significant inverse correlation between age and change rate of BMD was found at L2-4, but not at the proximal femur, in premenopausal women. In postmenopausal women, there was a significant association between body weight (BW) change and change rate in BMD at L2-4, femoral neck, or greater trochanter. This association was not found in the premenopausal group. These results suggest that effect of menopause on BMD may be different in individuals and sites of the skeleton. BW change may affect change in BMD in postmenopausal women.(ABSTRACT TRUNCATED AT 250 WORDS)