Since the early 1960s, small organic molecules derived naturally from microbes and plants have provided a number of useful cancer chemotherapeutic drugs. The search for naturally occurring lead compounds of this type has continued in recent years, with the constituents of marine fauna and flora as well as those of terrestrial microorganisms and plants being investigated for their anticancer activities. In the present short review, selected novel compounds that have been obtained from organisms of diverse biological origin, or their derivatives, are discussed in terms of their potential use as cancer chemotherapeutic agents. Such promising lead compounds tend to generate considerable interest among scientists such as synthetic organic chemists and biologists. Consequently, the supply of a given precious natural product sample may be enhanced, and it may be possible to determine a preliminary notion of structure-activity relationships and of its potential mechanism of action.