The optimum dose and duration of treatment with thalidomide for relapsed or refractory multiple myeloma are not known. Long term responses were seen in 5 patients given low doses of thalidomide (100-200 mg) with or without pulsed dexamethasone, for between 48 and 108 weeks. The responses were sustained for between 23 and 67 weeks after stopping treatment. We recommend that the lowest effective dose (LED) and optimum duration of therapy with thalidomide should be determined within the framework of a well conducted clinical trial in order to answer these important questions.