Estimation of age at death from human bones in legal medicine or in anthropology and archaeology is hampered by controversial results from the various macroscopic and histological techniques. This study attempted an estimation of age at death by histomorphometric analysis, from the fourth left rib adjacent to the costochondral joint in 80 forensic cases. Use of the picrosirius dye provided a reliable staining of the decalcified paraffin-embedded ribs. The total bone cortical area, the major and minor diameter as well as the area of the Haversian canals, the osteon areas of intact and remodelled secondary osteons, the area of non-Haversian canals were evaluated by means of image analysis, and derived parameters were calculated on both the internal and external sides of the rib. Most of the variables exhibited consistency between three different observers. Noteworthy, morphometric measurements in the internal cortex of the rib showed less variability than in the external cortex. Finally, discriminant statistical analysis from the 80 cases in this study indicated that the osteon population density was virtually sufficient to significantly discriminate between three groups of age: 20-39 (adulthood), 40-59 (middle age) and a group superior to 60. A subsequent blind evaluation of ten new subjects satisfactorily classified seven subjects out of ten within the three age groups. These results make feasible a larger study aimed at characterization of the practical relationships between bone tissue histomorphometry in ribs and chronological age in forensic cases.