Aminopterin (4-a m i n o-pteroylglutamic acid) is a potentially dangerous drug. It can favorably affect the lesions of psoriasis regularly, but the range between beneficial and toxic doses is narrow. The possibility of irreversible bone marrow aplasia is of chief concern in toxicity. Gubner1 has shown, however, that administration of the drug in conservative doses to nonleukemic individuals does not provoke such a disastrous complication. He has made the following observations: significant changes in psoriatic lesions were observed regularly in all patients (a total of 13, of whom 7 had associated arthritis) who were given Aminopterin. The dosage was 1.5 to 2.0 mg. daily, the total dose varying in individual cases from 14 to 140 mg. in from 10 days to nine months. Scaling stopped between the 5th and 10th days. Several patients had hemorrhagic crusting in the lesions at the time of improve