This study was undertaken to compare the effects of alendronate and risedronate on bone mineral density (BMD) and bone turnover markers (BTMs) in late Postmenopausal women with osteoporosis. Thirty women older than 60 y of age were randomly assigned to receive alendronate 10 mg (n=16) or risedronate 5 mg (n=14) on a daily basis. The patients were followed every 3 mo for 12 mo. BMD measurements were taken at baseline and at the end of the study, and BTMs were measured at 3-mo intervals. By the end of the study, there were statistically significant increases in BMD in both groups at all sites at which they were measured (P <.001). However, these differences were not statistically significant between groups. By the end of the study, all BTMs had decreased significantly and to a similar extent in both groups. The most significant change was observed in the third month of the study. A negative correlation was noted between percentage change in bone-specific alkaline phosphatase and femoral neck BMD (r=-0.467). This study reported no difference between the 2 drugs in their effects on BMD and BTMs.