Trabecular bone volume and trabecular connectivity (trabecular bone pattern factor) of edentulous mandibles were examined using undecalcified bone sections from the region of the 1st premolar to investigate atrophy-related changes in mandibular cancellous bone. The mean trabecular bone volume was 21.8% in female mandibles and 36.6% in male mandibles. The mean trabecular bone pattern factor was -0.22 mm-1 for female mandibles and -2.29 mm-1 for male mandibles. The difference between the sexes was statistically conspicuous for both parameters, but did not attain statistical significance. A notable fact was the extreme range of variation in both trabecular bone volume and trabecular connectedness. A difference of 65% between the highest and the lowest trabecular bone volumes measured in the present study (min, 7.6%; max, 73.6%, both male) reflects the possible variation in trabecular density of edentulous mandibles.