Treatment options for patients with myeloma who relapse after allogeneic stem cell transplantation are limited. Thalidomide, an antineoplastic agent, has been shown to be effective in multiple myeloma through proposed mechanisms that may include angiogenesis inhibition. Herein we report successful thalidomide treatment of four patients who relapsed following allogeneic transplantation, three of whom had predominantly extramedullary relapse. Thalidomide was well tolerated in all patients; in two patients interferon-alpha was subsequently added to thalidomide as maintenance therapy without worsening graft-versus-host disease. We suggest that extramedullary myeloma is particularly sensitive to thalidomide, speculating that growth biology may in part be dependent on angiogenesis.