 This is a phase III study of perifosine in combination with bortezomibwith or without dexamethasonefor patients with relapsed or refractory multiple myeloma previously treated with bortezomib. The current protocol will enroll patients with relapsed or refractory multiple myeloma who have been previously treated with bortezomib. The patients will be treated with perifosine, 50 mg or 100 mg qhs, in combination with bortezomib to determine if there is any preliminary evidence that the addition of perifosine improves the outcome for these patients. Previous treatment with perifosine will be allowed in this study. Patients progressing on treatment with perifosine and bortezomib will receive dexamethasone 20 mg on days 1, 2, 4, 5, 8, 9, 11, 12, 15, 16, 18, and 19 of each 21-day cycle in addition to bortezomib and perifosine. 