To determine whether personal history of lactation in premenopausal women influence bone mineral density, a cross-sectional study was conducted. One hundred eighty-four premenopausal women were selected from women who had been checked for bone mineral density by dual energy x-ray absortiometry in lumbar spine, femoral neck, Ward's triangle, and trochanteric site at general hospitals in Seoul and Pusan. They completed a questionnaire including life style factors and reproductive history. In the data analysis, Pearson correlation coefficients were used to test any association between individual variables and bone mineral density and a statistical comparisons between long term lactation(>24 months) and short term lactation(<24 months) were made by one way analysis of covariance. The results were summarized as follows: 1) There was no significant difference in the bone mineral density of the lumbar vertebrae in premenopausal women between the long term lactation group(>24months) and the short term lactation group(<24months). 2) There was no significant difference in the bone mineral density of the femur neck, Ward's triangle, and trochanteric site in premenopausal women between the long term lactation group (>24months) and the short term lactation group (<24months). Considering these results, we suggest prospective studies that measure bone mineral density before and after, in addition to those during lactation. We also suggest the further study with premenopausal women less than 35 who have achieved peak adult bone mass.