We report the first administration in Australia by ambulance officers of the Commonwealth Serum Laboratories' Chironex fleckeri antivenom, in two separate, major, potentially life-threatening Chironex envenomations. In both cases, the antivenom was effective in helping to relieve signs and symptoms (including pain). This antivenom still is the most specific part of the treatment of a major Chironex fleckeri sting after stabilization of the airway, breathing and circulation. The additional use of verapamil may contribute to the prevention of some of the cardiac complications that result from the direct effects of the Chironex venom.