In the metropolitan slaughterhouse, Shibaura, Tokyo, the first case of swine toxoplasmosis (TP) was reported in December, 1959. After that, 3 cases were recorded in 1960, 12 cases in 1961, and 27 cases in 1962.Of these cases, seven were detected in the antemortem examination from among 70 pigs shipped from Niigata Prefecture in November, 1961. The other cases were found in the postmortem examination from among hogs shipped from different prefectures all over the country.The antemortem signs of TP consisted of a high temperature of over 41°C, purpura in the auricle and hypogastric region, and sometimes dyspnea. The white blood cell count was in a range of 11, 000 to 13, 000. A slight shift, to the left was seen. Intradermal toxoplasmin test was negative in all the clinical cases, which, however, gave highly positive pigment tests on serum. These results provide helpful information on the antemortem diagnosis of TP.Postmortem changes were a little more pronounced in the clinical cases than in those found infected at autopsy. They included petechiae in the apical lobe of the lung, cloudy swelling of the liver, swelling of the splenic follicles, and lymphadenopathy of these organs. Histopathologically, perivascular cell infiltration, proliferation of glia cells hemorrhagic catarrh in the pulmonary alveoli, focal necrosis of the liver, and atrophy of follicles in the lymph node were observed.