This is a critical review of our current understanding of camptothecins, their shortcomings, and of the possibilities for improving their clinical performance. The authors discuss new camptothecin analog development, drug delivery issues for optimizing their anticancer activity, and their potential use in a variety of different cancers. Additional chapters describe what is known about the biochemistry, the pharmacology, and the chemistry of the camptothecins, including the mechanism of topoisomerase and how camptothecins poison this enzyme, the use of animal models in defining the anticancer potential of camptothecins, and the question of camptothecin resistance.