Treatments effective against multiple myeloma may be useful in primary systemic amyloidosis (AL). Thalidomide is active in myeloma. Results of the first 12 patients enrolled on a phase II trial of thalidomide for AL are presented. Progressive edema, cognitive difficulties, and constipation occurred in approximately 75%; dyspnea, dizziness and rash in 50%. Five developed progressive renal insufficiency. Deep venous thrombosis and syncope each occurred in two. Median time on the study was 72 days, range was 25 to 333 days. All 12 have withdrawn from the study (side-effects, 6; progression, 4; and death, 2 patients). AL patients do not tolerate high dose thalidomide.