Inflammation was induced in rabbits by intracutaneous injection of lysosomal particles prepared from guinea pig leukocytes. As far as the proinflammatory activity of lysosomal particles is concerned, when assessed by leakage of intravenous dye (5% Evans Blue), intact lysosomes were more potent than the broken ones, the activity was optimal 90 min after injection, and 0.04 μg of lysosomal protein can induce the inflammation. The anti-inflammatory potency of betamethasone 17, 21-dipropionate against the inflammation was higher than that of hydrocortisone acetate.