Benign prostatic hyperplasia is a primarily non-inflammatory enlargement of the prostate due to proliferation of its epithelial and mesenchymal structures. These physiological alterations can be found in more than 95 % of aged intact male dogs, but common clinical symptoms as serosanguineous urethral discharge, haematuria, flattened faeces, constipation and tenesmus are only present in a few of them. In addition to surgical castration, hormonal suppression of testicular function with GnRH-depot-analogues, inhibition of the 5alpha-reductase or peripheral androgen action with anti-androgens are available today. This enables the clinician to find the optimal therapeutic strategy for each patient.