This study compared SEM appearances of endosteal and periosteal surfaces of anorganic femoral diaphyses from three groups of adult male rats: (1) control; (2) castrate (osteoporotic), and (3) castrate + injections of dichloromethylene biphosphonate (Cl2 entrances; (2) area of vascular canal entrances; (3) number of osteoblast lacunae, and (4) percent area of bone surface types. Endosteal surfaces from untreated osteoporotic rats had significantly more osteoblast lacunae, larger vascular canal entrances, and less resting surface than those of the other groups. There were no differences in endosteal surfaces between controls and Cl2MBP-treated castrates. Periosteal surfaces demonstrated no significant differences in percent area of bone surface types between groups, untreated castrates had more osteoblast lacunae than other groups, and vascular canal entrances were smaller in castrate groups than in controls. Castrates treated with C12MBP had significantly fewer periosteal vascular canal entrances, and many canal entrances and osteoblast lacunae appeared to be plugged with mineral deposits when compared with the other groups. The results indicate that C12MBP treatment prevented endosteal bone surface changes that occurred with castration osteoporosis, and may have disrupted normal vascularization on periosteal surfaces.