This communication reports a partially reversible chemical immobilization protocol used for translocation and veterinary care in giant otter (Pteronura brasiliensis; GO). Six GOs (three males and three females) weighing 24.8 +/- 4.0 kg (mean +/- SD) and ranging in age from 16 to 42 mo old were anesthetized with an i.m. combination of medetomidine (29 +/- 3 microg/kg) and ketamine (3.9 +/- 0.4 mg/kg). To perform all procedures, two otters required an additional dose of ketamine (1.5 mg/kg). Anesthesia was reversed with atipamezole i.m. (147 +/- 14 mg/kg). The mean induction time and recovery times were 12 +/- 5 and 4 min (range, 0-9 min), respectively, with an anesthesia time of 47 +/- 16 min. According to these results, the combination of medetomidine (30 microg/kg i.m.) and ketamine (4 mg/kg i.m.) is a reasonable choice for inducing anesthesia in GOs.