The term “ecocide” was first coined to categorize massive destruction of the environment in war. If the sheer scale of the harm done be the distinguishing feature of ecocide, it is contended that the term may justifiably be applied to peacetime activities that destroy or damage ecosystems on a massive scale. The author shows that, although ecocide has a long history, it had little impact on international law until the advent of catastrophic oil spills at sea, nuclear accidents, long-range air pollution, and the threat of global warming. Then the international community began to demonstrate a growing concern, but the measures undertaken in response may already be too little and too late. The concluding part of the article deals with the more radical legal remedies (such as treating ecocide as an international crime) that may be needed to avert the threat of ecocide.