This study was carried out to investigate the prevalence of antibody against Toxoplasma gondii in the dog by Latex agglutination test and Indirect fluorescent antibody test. Two month-old dogs were infected intraperitoneally with T gondii to observe histopathological and immunohisto-chemical changes. Results obtained through this experiment were summarized as follows ; 1. Among the serum samples of 163 heads of the dog, 10 samples(6.1%) were positive. 2. In the sex, 6 heads (7.1%) out of 84 female dogs and 4 heads(5.1%) out of 79 male dogs were positive. However, there were no significant differences between the male and female. 3. Overall proportion of agreement between indirect fluorescent antibody and Latex agglutination test in 163 sera of dogs was 97.5%. 4. When 2 month-old dogs were infected intraperitoneally with T gondii, main clinical signs were intermittent fever, dyspnea, diarrhea. In general, the infected dogs recovered closely on the 11th day of post-inoculation. 5. At necropsy, petechial and ecchymotic hemorrages and swelling in small intestine, lung, spleen, liver and kidney were observed. 6. In histopathological observation, interstitial pneumonia, hyperemia and hemorrhages in lung were observed. Focal necrosis of hepatocytes, the neutrophil and basophil in the renal tubular epithelium were observed. 7. By immunohistochemical staining using Vectorstain ABC kit, the positive cells were recognized in the lung and the liver. 8. By indirect fluorescent antibody test, the Toxoplasma antibodies in the infected dogs were detected on the 15th day of postinoculation.