A survey was done of aging changes in compact and trabecular bone. During the past decade, noninvasive methods have demonstrated similar results for compact bone in large samples. Aging decreases of 3%/decade begin at about age 40 in both sexes and continue, but in women, an additional loss occurs after menopause, bringing their total rate of decrease to 9%/decade between ages 45 and 75. Results on trabecular bone loss are more variable, the majority indicating a slightly lower rate of loss (6% to 8% decade), beginning in young adulthood (20 to 40 years) in both sexes. These findings suggest that the common assumption about a large ongoing loss of trabecular bone after menopause may be erroneous. These assumptions are examined, as are the implications of the findings for calcium metabolism, anatomical correlations and fracture incidences.