We have experienced two cases of anaphylactoid reactions following intravenous methylprednisolone sodium succinate administration. They had neither asthmatic nor other allergic histories. The first case was a 45-yr-old man. In addition to the antigenicity of hydrocortisone itself, it is suggested that administration speed was so fast that its side effects were intensified. The second case was a 10-yr old girl. Succinate ester was thought to be the cause of her allergic reaction (urticaria). It is also possible that her hypersensitivity to steroids was dose-dependent.