Twenty-seven adult male southern elephant seals were immobilised to enableattachment of satellite transmitters and to obtain tissue samples. Large AnimalImmobilon (LA Immobilon) was injected remotely to achieve initial sedation(x=0,0009 mg/kg etorphine; 0.0037 mg/kg acepromacine) while ketamine wasinjected manually on demand to maintain narcosis (x=81 min). The total dosages(x=1,7 mg/kg) of ketamine required were negatively correlated with those ofLA Immobilon (p < 0,01). The dosages of LA Immobilon were approximately15 to 30 times lower than recommended for other large-sized mammal species,and the therapeutic range was low. Nine cases required the application of theetorphine-antidote Large Animal Revivon (x=0,0052 mg/kg diprenorphine) injectedintraveneously (n=3), intramuscularly (n=5), or sublingually (n=1). LA Immobilonappears to be useful to attain immobilisation in adult male southern elephantseals by remote injection owing to its high potency and hence small volume required.It must, however, be used sparingly and ideally for initial sedation due to its potentialdanger and narrow therapeutic margin.