The category of both lesions of so-called periarteritis nodosa and allergic angitis is still not clear, although recent medical lilerature contains frequently reference to numerous reviews of the pathology of vascular changes. The author investigated generally, type classification of the angitis that he could produce in fact by the twice intravenous injections of the large amount of horse serum (10 ml/kg) into the rabbits, and formal genesis of it in tracing of I^131 labeled antigen. Though angitis may not only develop in serum sickness but in drug allergy, the experimental proof has not yet been obtained. The author put to the test using Thiasin, Cortisone and Penicillin as inducing substance into the sensitized rabbits. 1) "Typical allergic angitis" was produced experimentally in the heart of numerous rabbits by twice intravenous injection of the large amount of horse serum. The various stages in the development of vascular lesion were observed histologically and with technique of radioisotope from the time of their initiation until 33 days later. 2) Vascular lesions were found mainly in the arterioles and small arteries, while the larger arteries of the muscular type were frequently involved. In examination of the histological sections, the bascular lesion bear a remakable resemblance to typical periarteritis nodosa, on the other hand showed various type of arteritis. 3) Allergic angitis in this investigation can not be differentiated from experimental periarteritis nodosa by Zeek. The difference are as follows: In allergic angitis, a) Distribution of vascular lesion is only in the heart. b) Time till occurrence of fully developed lesion with fibrinoid change is earlier than PN. c) Remarkable proliferation of fiblobasts in vascular wall and aneurysma are absent. 4) Distribution of inducing antigen in experimental animal was traced by radioisotope I^131, In the heart at first day after injection of inducing I^131 labeled antigen, activity values showed lower values than another organs, but about 3 times that of the control. 5) Antigen in the tissue of the heart was traced by micro-autoradiograph. The black granular silver deposits were recognized according with the site of early lesions of both outer media and inner adventitia. It is logical to believe that initial vascular change begins at that both regions simulataneously, and perivascular inflammation is not simple reparative inflammation following the lesion of the media, it shows probably direct reacion for allergic agent. 6) Continued injections of Thiasin, Penicillin and Cortisone into sensitized rabbits gave rise to thickening of intima in the heart vessel. Continued injections of penicillin as inducing substance into sensitized rabbits gave rise to angitis of media-adventitia type in the heart vessel.