A dog which was hospitalized to Veterinary Teaching Hospital, College of Veterinary Medicine, Jeonbug National University on December 28, 1988 was revealed severe anemia: hemoglobinuria and weakness. In the inspections, abdominal pain and spleno megaly at the ventral abdomen were detected by palpations. In the examinations of blood, the obtained results were summarized as follows: Babesla spp. was identified on the blood smear stained with Giemsa. The Babesia spp. was assumed to the Babesia gibsoni for the their small size and pleomorphism such as comma form, ring form and dot form. In the blood examinations of the patient, Ht: 22.5％, RBC:354${ imes}$10$^4$/${mu}ell$, Hb: 8.8g/dl, serum protein: 8g/dl, and WBC count was 21, 425/${mu}ell$. In the chemical examinations of serum, the value of AST(GOT) was 30iu and ALT(GPT) was 20iu, respectively. The blood sugar was 60mg/d1. In the urine test, urine protein was 30mg/d1 and the hemoglobin In the urine was the ＋＋＋ and occult blood reaction(Benzidine test) in the feces was ＋＋＋. Splenomegaly was confirmed by X-ray examination. To confirm for the Babesia spp. infection, 5ml of the whole blood of the patient(3％ of Parasitized erythrocytes) were inoculated into the cephalic vein of the two normal dogs. In the blood of experimental dogs which were inoculated parasitized blood, Babesia spp. was detected in the two doss and pleomorphic parasites were observed, too. In the blood examinations of No. 1 the Ht and RBC were decreased to 6.8％ and 52${ imes}$10$^4$/${mu}ell$, respectively. WBC count was 10.600/${mu}ell$ and serum protein was 6.8g/dl. The rates of parasitized erythrocytes were 15％ in the experimental dog. Also ＋＋＋ of the hemoglobin was detected in the urine. In the X-ray examination, splenomegaly was comfirmed and it was confirmed by autopsy of the experimental dog(No. 1).