This 2 arm study will compare the efficacy of intravenous Bondronat with that of zoledronic acid in patients with malignant bone disease experiencing moderate to severe pain. Patients will be randomized to receive either Bondronat (6mg iv on days 1, 2 and 3 and then every 3-4 weeks) or zoledronic acid (4mg iv on day 1 and then every 3-4 weeks). The anticipated time of study treatment is 6-12 months, and the target sample size is 100-500 individuals.

Inclusion Criteria:

• patients with malignant bone disease;
• patients with moderate to severe pain.

Exclusion Criteria:

• patients who have received a bisphosphonate within 3 weeks from the signing of the informed consent;
• patients receiving concurrent investigational therapy, or who have received investigational therapy within 30 days of the first scheduled day of dosing;
• untreated esophagitis or gastric ulcers;
• recent or pre-scheduled radiotherapy to bone;
• patients who are pregnant or breast-feeding.