This review summarizes basic pathophysiology, epidemiology, classification and theories on the etiology of osteoporoses. Diagnostic, preventative and therapeutic aspects are discussed including the use of hormones and hormone analogues (estrogen, progestins, calcitonins, anabolic steroids), calcium, fluoride, bisphosphonates, vitamins D and their metabolites and the recently proposed "coherence therapy". Reference is made to new compounds under study including imidazoquinazolinones, methylxanthines and benzothiophenes.