It is given a description of the clinical case of a 10 year old mixed-
breed male dog. Its clinical symptom was an acute retention of urine c
onditioned by a cystic prostatic hypertrophia. Additionally the dog sh
owed a not insulin dependent diabetes mellitus. A small tumor, histolo
gically identified as a seminoma, was found in the right testicle. The
blood-glucose concentration normalised and the prostata reduced in si
ze after the castration of the dog. In the literature we found a corre
lation between a production of estrogenes by the seminoma and the type
II diabetes mellitus.