The anatomy of the remodeling sites in bone is only partly reflected by random histologic sections. This study is aimed at reconstructing the three-dimensional morphology of the osteons in human trabecular bone from serial sections of decalcified tissue. The osteons resembled broad bands, which were made up of parallel lamellae, bounded on one side by the marrow surface and on the other side by an irregular cement plane. The mean thickness was much less (<0.2) than the mean extent in the other dimensions. The plate may, therefore, be used as the morphologic model for stereologic studies. The plates were curved and irregular. One three-dimensional osteon can, therefore, give rise to a varying number of profiles in a single random section. The two-dimensional profiles, which are of unequal surface extent, are thus not appropriate sampling units for morphometric studies of, e.g., osteon thickness, osteoid thickness, or calcification rate in trabecular bone. When estimating thickness the number of measuring sites should be sampled proportional to the surface extent of the profiles.