Natural products have been regarded as important sources that could produce potential chemotherapeutic agents. Over 50% of anticancer drugs approved by United States Food and Drug Administration since 1960 were originated from the natural resources, especially from terrestrial plants. Based on cytotoxicity bioassay, over 400 compounds have been isolated from plants, marine organisms and microorganisms from the period of 1996 to 2000. Recently, interest of natural product research has slowly moved to marine organisms. As a result, almost 50% of reported cytotoxic compounds were isolated from marine organisms such as sponges and corals. Also, traditional cytotoxic compounds of acetogenins, alkaloids and terpene skeletons have been reported continuously. In this review, we will present the cytotoxic compounds obtained from natural sources from 1996 to 2000, and the structures and cytotoxic activity of natural compounds isolated from territorial, marine and microorganism resources.