Venomous organisms are usually resistant to their own venoms, and utilize mechanical behavioral means to resolve intra-specific conflicts, such as those occurring over territory, mates or social status. The present study deals with a venom apparatus, which has been specifically designed for conspecific aggression, by the aid of a unique pharmacology. Actinarian sea anemones such as Actinia equina utilize vesicular organs termed acrorhagi in order to deter conspecific territorial competitors. The territorial aggression was shown to be performed by the aid of acrorhagial cnidocysts, which inflict localized tissue necroses on the body of the approaching-threatening anemone. In view of the fact that sea anemones were shown to resist mechanical injuries and their own cytolytic, necrosis-inducing pore-forming substances-the above acrorhagial injuries are ambiguous. Using an electrical device to collect acrorhagial cnidocyst-derived venom, we have shown that the venom is devoid of paralytic-neurotoxic activity, contains heat denaturable hemolytic polypeptides of a low molecular weight and is capable of inducing intracellular formation of reactive oxygen species (ROS) upon medium application to various cultured cells. The ROS formation phenomenon provides a reasonable pharmacological solution to the, above-mentioned, paradoxical conspecific self-intoxication by triggering a preexisting global endogenous mechanism of oxygen toxicity common to aerobic organisms.