Histomorphometric analysis of mandibular specimens has been performed in order to demonstrate possible sex and age differences in percent bone mass and bone activity in the mandible. The material consisted of 32 autopsy specimens from the right premolar region of the mandibular body in subjects with sudden unexpected death and without known bone disease. The subjects were divided in a young group (20--43 years of age) and an old group (60--90 years of age); each group consisted of eight females and eight males. Microradiograms of buccolingual ground sections of 100 micron were used. Quantitation of (1) percent bone area of cortical and trabecular bone and (2) total bone surface/bone area and resorption surfaces/total bone surface in trabecular bone, were done by electronic point-counting. The analysis did not reveal any significant sex or age differences in the trabecular bone with respect to percent bone mass, trabecular coarseness and bone activity. In the buccal and lingual cortices a significant age difference was demonstrated, but there was no sex difference in percnet bone mass. Cortical porosity in mandibles clearly increases with increasing age, but seems to be independent of sex.