The aim of this study was to determine the therapeutic Success Of the medical treatment of pyometra with the antigestagen aglepristone and to document the recurrence rate in relation to the time interval after treatment with antigestagens in cats. Ten cats, 2-13 years of age and nulliparous were used in the Study. The cats were treated with aglepristone at a dose of 10 mg/kg body weight subcutaneously on days 1, 2, 7 and 14 (if not cured). In addition, trimethoprim/sulphadoxine was also administered at a dose of 15 mg/kg body weight subcutaneously once a day for 7 days. Nine out of the 10 cats responded well to treatment. No recurrence was observed in a follow-up period of 2 years. No side effects were observed. The data suggest that aglepristone treatment is a promising approach for the medical treatment of pyometra in cats. (C) 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.