In this study, the efficacy of aglepristone and/or intrauterine antibiotic administration for the treatment of bitches with cystic endometrial hyperplasia/pyometra complex was investigated. Twenty-four bitches (5-12 years old) with the diagnosis of pyometra were treated at the University of Kafkas and at Istanbul University. The diagnosis of pyometra was established on the basis of the results of clinical, ultrasonographic and vaginal examinations, the haematological and biochemical findings and the history data. In Group I (n = 13), aglepristone (Antiprogestin, Alizine®, Virbac, France; 0.33 ml/kg, s.c.) was administered on days 1, 2, 7, and 14 (day 1: diagnosis). In Group II (n = 11), intrauterine antibiotic treatment was performed according to the antibiogram on days 1, 2, 4, 6, 8 in addition to aglepristone given as in Group I. Clinical and ultrasonographic examinations, haematological results and occurrence of oestrous cycles revealed that the ratio of effectively treated bitches was 6/13 and 9/11 in Groups I and II, respectively.