Stilbestrol given intramusc. and intra-ven. to 4 dogs in doses of 10-20 mg./day caused increased capillary fragility, prolonged bleeding and clotting times, and reduced platelet counts. A true purpura developed in 14-25 days. It was quickly cured by oral doses of 200 mg./day of a-tocopherol (ephynal, Hoffman-LaRoche). Five human thrombocytopenic cases were cured with 200-400 mg. of ephynal/day, in 7-14 days, but the treatment had to be continued indefinitely.