Osteoporosis is the most common metabolic bone disease. It is characterized by low bone mass and micro-architectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. Osteoporosis is an asymptomatic disease and is an important public health issue because of its clinical expression in age-related fractures. In Iran it is estimated that the prevalence of osteoporosis among women who older than 50 years old is 6 percent which is less than other countries such as Canada and Japan . The estimated lifetime risk of hip fracture for white women at age 50 years is about 16 percent (versus five percent for men). The incidence of fall related hip fracture in Iran in 2003 in male and female was respectively 20.6 and 17.5 per 100,000 person-year which is increased significantly in old people. Nowadays, several treatments are available and more are being developed. Currently available drugs are anti-resorptive which focus on decreasing bone turnover. Newer therapies with the aim of increasing bone formation are being studied. This document outlines all aspects of osteoporosis "especially in Iran "including risk factors, diagnosis, prevention and treatment.