Case 1. A 65-year-old man was diagnosed as having advanced prostate cancer in November 1997. Bony metastases were found in the thoracic spine and ribs, and the patient underwent external beam radiotherapy. In October 1999, 6 days after receiving his first infusion of pamidronate, he had a sudden onset of left orbital pain and then developed diplopia with upgaze. At examination, his corrected visual acuity was 20/20 OU. Confrontational visual field measurements were full to finger counting. Pupils were equal and round without a relative afferent pupillary defect. Ptosis and proptosis were absent. Elevation of the left eye was mildly restricted, and a 3–prism diopter left hypotropia was measured in upgaze. Upper and lower eyelid edema, conjunctival injection, and mild chemosis were present in the left eye. No anterior segment or vitreous inflammation was observed. The results of a dilated fundus examination were normal. Magnetic resonance imaging of the brain and orbits with gadolinium contrast showed no evidence of a metastatic lesion. The patient was treated with oral prednisone (80 mg/d), experienced prompt resolution of his symptoms, and received no further doses of pamidronate.