This compilation is divided into four parts. Part 1 thoroughly reviews the problem of osteoporosis. The authors and chairman of this section do not agree as to the cause of the condition, but the vast amount of investigative research that is presented permits an intelligent clinician to attain a better understanding of the etiology of osteoporosis as well as a sound clinical approach. Part 2 covers the current understanding of the chemistry and morphology of bone. Part 3, "Ultrastructure of Bone," is of special interest to clinicians and to investigators because of the excellent illustrations of electron-micrographs and of the use of autoradiography in the study of bone. Part 4 reviews and brings up to date the present status of parathyroid and vitamin D physiology. The chapter on citrate metabolism is of special interest as the importance of such metabolism has not received much recognition in the clinical journals.