Radiographic, historical, clinical signs, and surgical and histopathologic findings of six dogs with diagnosed cystic uterus masculinus are given. The condition was seen in aged dogs between 4 and 15 years (mean of 8.8 years). There was no breed predisposition, although the larger breeds were involved in this study. The predominant clinical signs were constipation, dysuria and anuria. Lateral survey recumbent abdominal radiographs coupled with negative‐or positive‐contrast cystography were useful in delineating the bladder and the urethra, thus revealing the smooth‐contoured, asymmetrical fluid‐filled viscus in the caudal abdomen. The bi‐horned cysts were connected to the dorsal urethra through a short blind‐ending pedicle. The nonseptic, aspermic, cystic fluid averaged 146.7 ml (range of 100–200 ml). The predominant epithelial lining cells seen were simple columnar to pseudostrati