Abstract: It is well known that bone mass density decreases with age. Age‐related bone mass loss is ascribed to several factors. Nonenzymatic glycation has been proposed as a new potential factor in the loss of bone during aging. In this study we evaluated the concentration of pentosidine, an advanced glycation end product, in cortical and trabecular bone and in the plasma of subjects undergoing orthopedic surgery. The relationship between these parameters and a clinical index of osteoporosis was also studied. Samples of bone and plasma of 104 nondiabetic subjects (74 women and 30 men), 72 ± 1 years old, were studied. Pentosidine was determined by HPLC after decalcification and hydrolysis. The radiologic Singh index was evaluated blindly by orthopedic surgeons to provide the degree of osteoporosis. Pentosidine concentration of cortical bone shows a significant exponential increase with age (r= 0.610, P < 0.001). This increase, however, is not seen in the trabecular bone, which is characterized by a large spread in the data. Interestingly the concentration of cortical pentosidine is also related to the Singh score (rs=−0.274, P < 0.01). Plasma pentosidine has a significant exponential correlation with age (r=+0.339, P < 0.001) and a linear correlation with the cortical bone pentosidine (r=+0.248, P < 0.05). This study demonstrates that pentosidine increases exponentially in cortical bone during aging, and is thus a good biomarker for the degree of bone mass density loss. The trabecular bone concentration of pentosidine is more variable, probably because of the turnover rate and the local environment; plasma pentosidine might provide information on the bone turnover rate.