In the 19 years since Gubner first treated psoriasis with methotrexate, its use has gradually become standard practice in the United States and throughout the world. Its effectiveness and the manifestations of acute intoxication are well established, but the safety of prolonged administration remains unknown. That protracted usage may be detrimental has been suggested by several reports from the United States and Europe which indicate chromosomal and hepatic damage in methotrexate-treated psoriatic patients. A report from Utah1 implicates methotrexate in pulmonary disease as well. The cytogenetic aspect has been recently investigated.2 Metaphase chromosomes were analyzed in a total of 6,200 leukocytes from ten healthy adults, nine drug-free psoriatics, and nine psoriatics who had received methotrexate over a long period. No biologically or statistically significant increase in chromosomal abnormalities could be detected in any of these patients. In addition, four of the nine patients who had received previous methotrexate