This paper reports in detail, for the first time, on two anesthetic procedures performed on a 15-yr-old, 530 kg, adult male Sumatran rhinoceros (Dicerorhinus sumatrensis). The anesthetic procedures were carried out in order to perform semen collection via electro-ejaculation, using well-established methods, and in order to examine and sample bilateral corneal opacities. Anesthesia for the first procedure was induced with a combination of 5 mg (0.0094 mg/kg) butorphanol tartrate and 5 mg (0.0094 mg/kg) detomidine hydrochloride administered intramuscularly. Subsequently, 0.74 mg (0.0014 mg/kg) etorphine and 3 mg (0.0057 mg/kg) acepromazine, with an additional 1.5 mg butorphanol (0.0028 mg/kg) and 1.5 mg (0.0028 mg/kg) detomidine, were administered intramuscularly. The second procedure was carried out using an intramuscular combination of butorphanol (0.019 mg/kg) and detomidine (0.019 mg/kg), followed by etorphine (0.0023 mg/kg) and acepromazine (0.009 mg/kg). During the second procedure, the depth of anesthesia was managed with very small, supplemental intravenous doses of 50 mg ketamine (0.094 mg/kg). Sequential arterial blood gas analysis demonstrated respiratory acidosis with hypoxemia. Heart rate and respiratory rate ranged between 60–74 beats per minute (bpm), and 10–20 breaths per minute, respectively. Reversal after 100 min, with the intravenous administration of 150 mg (0.28 mg/kg) naltrexone and intravenous 20 mg (0.038 mg/kg) atipamezole, was uneventful and rapid, with the animal standing after 2 min. This combination provides satisfactory general anesthesia in this critically endangered species and will facilitate veterinary management of this species in captivity.