The aim of the present study was to evaluate the effectiveness of delmadinone acetate (DMA) for the treatment of hypersexuality (HS) and benign prostatic hypertrophy (BPH), which are frequently observed in male dogs, for which no surgical treatment has been indicated. The study was performed with 21 intact male dogs that had HS (n = 12) and signs of BPH (n = 9). DMA (Tardak(R) or Tardastrex(R)) was administered subcutaneously to each dog at a dose of 3-5 mg/kg and was repeated 15 days later as a second treatment. DMA administration was repeated in some cases until the clinical signs disappeared. The successful recovery rate of HS cases was found to be 50% after a single application and 25% by the second and third applications. The mean "recovery periods" and mean "stable periods" of these 3 consecutive applications were found to be 5.83, 7.66, and 6.00 days, and 16.7, 18.7, and 20.0 months, respectively. With regard to BPH after consecutive applications, treatment success rates, mean recovery periods, and mean stable periods were 33.3%, 22.2%, 44.4%, 12.0, 11.0, 9.5 days, and >30, 12, and 13.5 months, respectively. DMA is clinically applicable as a therapeutic agent for HS and BPH cases; however, repeated applications were required due to temporary recoveries.