Ultrasonographic and vaginal cytologic examination were performed on a maiden 13- year bitch presented our clinics with the complaint of bloody-prulent vaginal charge, vulvar oedema and nymphomania for four months. There were anechogenic areas in uterine ultrasonography. It was observed cornified superficial epithels 100% on cytologic exams. Serum estradiol, progesterone and testosterone levels were 23.46 pg/ml, 0.030 ng/ml and 0.020 ng/ml respectively. Anemia and high WBC were observed due to persistent haemorragy and pyometra on bitch with CEH-pyometra. When it was measured the degeneration of liver and kidney, AST, ALT, ALP and urea were normal. For treatment, OHE operation was performed. During operation, ovarian cystes the biggest one was on the left ovarium (23x12mm) and 3-5 mm diameter on the right ovarium were seen. Moreover, the proliferation of left cornu uteri was more severe than other. In this case, formation of CEH-pyometra in ipsilateral cornu uteri cause of long and high estrogenic effect was observed clearly