The aim of this study was to establish the reference values of the bone mineral density (BMD) of the lumbar spine and the proximal femur in a normal adult female Puerto Rican population. In the selection of the population, exclusion criteria included diseases, use of drugs and toxic habits (smoking and alcoholism) known to affect bone and mineral metabolism. The study population comprised 131 healthy females, ages 20 to 69 years. Spinal radiographs were taken of women age 60 or more to exclude spinal defects or artifacts. The bone mineral densities were measured using the dual energy X Ray absorptiometer (DEXA, Hologic model 1000). The peak BMD was found in the lumbar spine at the age 30 to 39 years and at the age 20 to 29 years in the femoral neck, trochanter and Ward's triangle. The decrease in BMD from peak values to those at age 60 to 69 years were 18% for the lumbar spine, 16.3% for the femoral neck, 30.1% for the Ward's triangle and 12.4% for the trochanter. The major fall in the BMD was related to the menopause and compares with that of other series. There was no statistical difference from Hologic reference values in a mixed population of the USA.