Full-thickness biopsy specimens of iliac bones were submitted to morphometric analysis of intratrabecular osteons to study whether and how much the number and density of osteons increase in some metabolic bone diseases such as osteomalacia (OM), primary hyperparathyroidism (PHPT) and renal osteodystrophy (ROD). The biopsies were taken from 16 patients with OM of various causes, 18 with PHPT, 12 with ROD, and from 41 control cases. All the specimens were methacrylate-embedded, sectioned undecalcified and stained with solochrome cyanine or HE. Morphometry included measurements of the density of osteons and the volume of bone and osteoid, partially assisted with a semiautomatic digital image analyzer. Intratrabecular osteons were found to be more numerous in patients with metabolic disorder than in control. It was shown by discriminant analysis that the elevated number of osteons/cm2 tissue area contributes to the differentiation of abnormal from normal bones. The presence of blood vessels in the osteons indicated the biological significance of osteon formation which extends the metabolic surface of trabeculae, providing a basis for trabecular hypertrophy.