This review details the contribution to modern medicine and pharmacy made by natural products and drugs derived from natural products, with an emphasis on essential medicines and new introductions to the market. Areas covered include recent advances in the development of drugs derived from marine organisms, microbes, terrestrial animals, and vascular plants, and current issues regarding botanical medicines. The role of natural products in drug discovery and development is evaluated, particularly with regard to their value as sources of drug leads with "drug-like" properties. A rationale for the success of natural products research in providing new drugs and drug prototypes is presented, drawing on lines of evidence from chemical informatics and chemical ecology. Several innovative strategies for natural products drug discovery and evaluation of botanical medicines are also reviewed.