During the period January 1993/December 1998, 15363 male dogs were referred to the Utrecht University Clinic of Companion Animals (UUCCA). Of these dogs, only animals with clinical signs of prostatic disease underwent diagnostic work up of the prostate. In 225 dogs prostatic disease was diagnosed. Diagnoses were made by means of cytological examination of fineneedle aspiration biopsies of the prostate or urine catheter aspiration biopsies taken under ultrasound guidance. A modified Menghini needle, 18/21 Gauge, was used (Teske and Nickel, 1996) for the fine-needle aspiration biopsy. In addition, another 206 male dogs were diagnosed as having prostatic disease based on cytological examination of specimens submitted by referring veterinarians. In all animals the following data were collected either from the medical records or by means of telephone inquiry: diagnosis of prostatic disease, age at diagnosis, breed, information on castration, and interval between castration and diagnosis of prostatic disease.