We will invite eligible subjects to participate in the study. We will offer patients who elect not to participate in the therapeutic trial the opportunity to have serial BMD measurements at the same intervals as treated subjects and to be followed as untreated controls. We will continue recruitment until we have randomized a total of 146 cardiac transplant recipients. We will perform bone densitometry at randomization (unless performed within the previous month) and at 6 and 12 months. We will obtain radiographs (x-rays) at randomization and will repeat them at 12 months to detect undiagnosed vertebral fractures.