Osteoporosis is a major public health problem in Iran. Bone densitometry is used to diagnose osteopenia and osteoporosis and if necessary, prevent bone fractures, especially that of femoral neck. Bone density is related to several factors including race, age, sex, environmental factors and nutrition. No comprehensive study has been performed in Iran, yet. Among the 10 to 75 year-old population living in Tehran, after excluding those who suffered from conditions affecting bone metabolism , 600 people were randomly selected from 50 clusters. All participants underwent a clinical examination and lumbar and spinal densitometry using DXA method. Prevalence of osteoporosis and osteopenia in women older than 50, was 28.1% and 53.3%, respectively. Prevalence of osteopenia and osteoporosis was higher in our study population. Peak bone density in the 25-35 -year-old population could be useful in policy-making for prevention and treatment of osteoporosis .