219 postmenopausal Chinese women with osteoporosis were randomized to receive one of two medications: a weekly dose of alendronate sodium with vitamin D3 (ALN/D5600) or a daily dose of calcitriol. The purpose of the study was to determine if ALN/D5600 provided greater benefits for bone mineral density and other measures of osteoporosis compared to calcitriol and to assess the safety of alendronate treatment. ALN/D5600 resulted in significantly greater increases in bone mineral density, serum 25(OH)D, and reductions in biochemical markers of bone turnover in comparison to calcitriol, at up to 1-year follow-up. ALN/D5600 also had a higher rate of drug-related adverse events, but the number of serious adverse events was similar between groups.