Four medetomidine/ketamine (M/K) doses (30 μg/kg/3 mg/kg; 40/4; 50/5; 60/6), administered by intramuscular injection, were evaluated for short-term immobilization of adult male variable flying foxes (Pteropus hypomelanus). The highest dose (60 μg/kg/6 mg/kg) produced a significantly faster induction (31±46 sec) than the lowest dose (30/3) (125±62 sec). The highest dose levels (50/5, 60/6) produced significantly longer immobilization times (52.5±25.7 min and 60.6± 20.8 min, respectively) than did the lower doses (30/3, 40/4) (18.8±8.7 min and 31.0±14.3 min, respectively). The dose at which 50% of the bats were immobilized for ≥30 min (ED₅₀) was approximately 40 μg/kg/4 mg/kg. This dose produced a mean immobilization time of 31±14 min, bradypnea and bradycardia. In conclusion, a M/K dose of 50 ug/kg/5 mg/kg is recommended for greater than 30 min of relaxed immobilization in free-living variable flying foxes and is sufficient for safe collection of samples.