To evaluate the effect of zoledronic acid on androgen deprivation therapy in patients with hormone-sensitive prostate cancer by measuring the percentage change in lumbar-spine bone mineral density (BMD) at 12 and 24 months.An open-label, multicenter, randomized, two-phase study was conducted in patients with hormone-sensitive prostate cancer (N = 200) receiving 10.8 mg goserelin acetate with or without zoledronic acid (4 mg intravenously) every 3 months. In phase I, patients were randomized to goserelin acetate alone or goserelin acetate plus zoledronic acid for 12 months. In phase II, patients receiving goserelin acetate plus zoledronic acid continued treatment for up to a total of 24 months, whereas patients receiving goserelin acetate alone were randomized to goserelin acetate alone or goserelin acetate plus zoledronic acid for an additional 12 months. Lumbar-spine, femoral-neck, and total-hip BMD were assessed at 6, 12, and 24 months. Additional assessments included height change, laboratory studies, bone scans, radiographs, and computed tomography scans.Significant BMD differences between patients receiving goserelin acetate alone and goserelin acetate plus zoledronic acid were observed at the 12-month (p