Patients receive phenylbutyrate IV continuously and sargramostim (GM-CSF) subcutaneously on days 1-7 and 15-21. Patients also receive oral dexamethasone on days 1-4 and 15-18. Treatment continues every 28 days in the absence of disease progression or unacceptable toxicity until complete hematologic remission is induced. Patients with stable disease at the end of 1 course receive at least 2 additional courses.