Inclusion Criteria:

- Patient age ≥18 years

- Undergoing allogeneic hematopoietic stem cell transplantation (HCT) from any stem
cell source with either a myeloablative or non-myeloablative conditioning regimen

- Bone mineral density measured by baseline pre-transplant DEXA scan in the osteopenic
range (defined as a T-score between -1 and -2.5 standard deviation (SD) at either the
lumbar spine or the proximal femur or both)

- Adequate renal function defined as: Calculated creatinine clearance of ≥ 60 ml/min
using the Cockcroft-Gault formula:

- Serum calcium (corrected) of ≤ 10.5 mg/dl

- Patients (male or female) of reproductive potential are required to use a medically
acceptable contraception while receiving zoledronic acid (if assigned study drug).

- Normal dental exam within the year prior to study registration

- Informed signed consent to participate in the study

Exclusion Criteria:

- Pre-existing metabolic bone disease including osteomalacia, hyperparathyroid bone
disease, osteogenesis imperfecta, Paget's disease, rickets, or hypoparathyroidism.

- Multiple myeloma

- History of nontraumatic vertebral compression fractures

- History of the following endocrine disorders - hyperparathyroidism, hyperthyroidism.

- Malabsorption syndrome including Crohn's disease.

- Chronic liver disease

- Concomitant regular use of phenytoin.

- Known hypersensitivity to zoledronic acid (Zometa) or other biphosphonates

- Biphosphonate therapy within the preceding six months.

- Current active dental problems including infection of the teeth or jawbone (maxilla
or mandibular); dental or fixture trauma, or a current or prior diagnosis of
osteonecrosis of the jaw (ONJ), of exposed bone in the mouth, or of slow healing
after dental procedures.

- Recent (within 6 weeks) or planned dental or jaw surgery (e.g. extraction, implants)

- Not pregnant or breastfeeding since zoledronic acid is classified as Pregnancy
Category C: risk in pregnancy cannot be ruled out. A negative pregnancy test is
required within 7 days of registration if pre- or perimenopausal (i.e., last
menstrual period within one year of registration). Because it is not known whether
zoledronic acid is excreted in breast milk, breastfeeding is not permitted while
receiving study drug.