Those aspects of bone histology and histomorphometry that need to be understood by clinicians to put histomorphometry into proper perspective are presented. An increasingly important component of the histologic diagnosis of the metabolic diseases of bone is the quantification of the various histologic features as seen in undecalcified bone biopsies. This article is intended to review some of the histologic features of the metabolic diseases of bone and their corresponding histomorphometric parameters as they are used in diagnosis. The methods of obtaining both direct and derived values as well as the reporting of the results are presented in detail.