• Chronic granulocytic leukemia in 21 patients was treated with Myleran. Significant remissions for periods up to 48 months were obtained in 17 patients, with restoration of the total white blood cell count to normal figures, improvement in the hemoglobin concentration, and disappearance of splenomegaly in 9 patients. Eight patients, however, showed less complete remissions in that maintenance therapy was required, and four patients with subacute or chronic forms of the disease were not helped. Myleran was also administered to 20 patients with various neoplastic diseases, but without effect. The usefulness of Myleran appeared to be limited to chronic granulocytic leukemia. Overdosage causes depression of the bone marrow, especially of platelet formation. Treatment with Myleran must be regulated with constant reference to the patient's hematological status. The recommended dosage on the basis of the foregoing observations is 10 mg. daily until the leukocyte count falls to 25% of its initial level; treatment is then suspended until the fall ceases and can be resumed later, if necessary, for a few doses until normal counts are reached. In some patients daily maintenance therapy with 2 to 4 mg. may be necessary.