The natural compounds that interfere with cellular DNA such as enediyne antitumor antibiotics might be important chemotherapeutic agents for the treatment of cancer. In this article, the pharmacology and anticancer activity of the enediyne antitumor agents that are approved for clinical use and undergoing pre-clinical or clinical evaluation are reviewed. Most enediyne compounds have shown potent activity against the proliferation of various cancer cells, including cells that display resistance to other chemotherapeutic drugs. Enediyne derivatives, such as an immunoconjugate composed of an enediyne compound and monoclonal antibody, reveal stronger activity and selectivity for human cancer cells. The mechanism underlying the anticancer activity of these enediyne antitumor agents may mainly lie in their generation of DNA double-strand breaks. Increasing evidence shows that the enediyne-induced DNA double-strand breaks can engage the activation of DNA damage response proteins, arresting cell cycle progression and eventually leading to apoptotic cell death. Continued investigation of the mechanisms of action and development of new enediyne derivatives and conjugates may provide more effective therapeutics for cancer treatments.