FLUOROURACIL has found a definite place in the treatment of advanced cancer, especially those tumors primary in the breast or colon. 1 Probably the most disturbing toxic manifestation of this drug is the development of severe and occasionally lethal granulocytopenia. Once this state has developed, opinions vary as to the best form of therapy that will ensure or aid in recovery. Antibiotics are usually given but then the question as to whether corticosteroid drugs should be administered is frequently raised. There is inconclusive evidence that corticosteroids will adversely affect myelogenous leukemia 2,3 and even less evidence that they will "stimulate" an already depressed or aplastic bone marrow 4,5 nearly devoid of granulocytes. The purpose of this study was to determine whether the concurrent administration of a potent corticosteroid drug (methylprednisolone) with conventional courses of intravenous fluorouracil would protect the bone marrow and other normal tissues from the toxic effects of