A total of21 female dogs, of different breeds and ages, with a clinical history of pyometra, and one apparently normal bitch, were subjected to ultrasound and hematological analysis, as well as macroscopic and histological examination of the uterine homs. Ultrasound analysis proved to be highly accurate for the diagnosis of pyometra in ali 21 dogs with clinical symptoms. The uterine horns of these animals were enlarged, and anechogenic and/or hypoechogenic, while in most cases the uterine walls were enlarged and hyperechogenic, with hypoechogenic rough endometrial surfaces, confirming the diagnosis ofpyometra. No uterine abnormalities were detected in the apparently normal case.