Nine marine otters (Lontra felina) were anesthetized 15 times with a combination of ketamine (5.3 ± 0.9 [range: 4.5–8.0] mg/kg) and medetomidine (53 ± 9 [range: 45–80] μg/kg) i.m. by hand syringe for the placement of radiotransmitters. Times to initial effect and induction period ranged from 1.1 to 5.0 min and 1.8 to 5.4 min, respectively. Minor complications did occur, including mild hypothermia in six otters and severe hypoxemia in one otter. After 34 and 63 min, anesthesia was antagonized with atipamezole (226 ± 29 [range: 179–265] μg/kg) and all otters recovered within 3.3–26.8 min.