In 1958, some cases of hog cholera were found at the Animal Quarantine Station at the port of Kobe. A positive diagnosis was made by inoculation of pigs and from histopathological findings. In inoculation tests, two experimental pigs which, had been inoculated with emulsified spleen and mesenteric lymph node of naturally infected pigs took an unusually long chronic course. One pig became moribund on the 72 nd day and the other died on the 54 th day following inoculation.The results of clinical, hematological, and pathological observations on the two cases were described in this paper.As main clinical signs, continuous mild fever of around 40°C, mucous excretion from the eyelids, constipation with nasty smell, and anorexia were observed since the early stage. Furthermore, coughing was seen in a later stage. Paralytic nervous symptoms appeared several days prior to death.In hematological examination, the two cases were lacking of definite signs of hog cholera. The appearance of immature granulocytes (myelocytes and -metamyelocytes) was slight and seen only in a later stage.At autopsy, hemorrhagic lesions in the visceral organs and lymph nodes were main findings. Histologically, the lesions consisted of aplasia and necrosis in the lymphatic tissue, hemorrhage, activation of the reticuloendothelial system, and proliferation of vascular connective tissue. These changes coincided with those of animals experimentally and naturally infected with hog cholera. The histological lesions of the two cases, however, were unexpectedly slight in spite of a very long course of disease. On the other hand, the severity of hog cholera lesions is generally parallel to the length of course in acute and subacute cases.Sasahara and Dunne divided hog cholera into four types peracute, acute, subacute, and chronic, from the length of course. The two cases reported here seem to be the first cases of chronic type which were observed in the laboratory in Japan.