Toxic dermatitis induced by 10-ethyl-10-deaza-aminopterin (10-EdAM), a novel antifolate. A new methotrexate analog, 10-ethyl-10-deaza-aminopterin (10-EdAM), was found to induce a particular form of skin toxicity different than the skin rash reported to result from methotrexate. At histologic examination, it was found to be a toxic dermatitis that clinically most often first appears on the lower legs but can occur anywhere in the body, especially if treatment is continued. Nine cases are reported. A specific risk factor could not yet be identified. Discontinuation of 10-EdAM administration leads to complete healing; concomitant corticosteroid treatment also induces healing. 