Osteoporosis maintains a special position in today's medicine, regarding both its growing incidence and its clinical and social consequences--fractures, leading to the loss of self-dependence, disabilities and higher mortality rates. It was thought for many years that osteoporosis affected mainly women after menopause. At present, it is known that the problem concerns men, as well. In the present review, similarities and differences between osteoporosis in either sex are discussed, concentrating on epidemiological and pathogenetic aspects, as well as on therapeutic differences.