This report is a review of the literature of marine natural product chemistry for 1996. Earlier reports published in this journal cover the period from 1977 to December 1995. Over the past two years, marine natural product chemistry has graduated from an expanding to a mature field. Approximately the same number of new compounds have been described but more marine natural products are being selected for synthesis and for in-depth investigations of their biological properties, both from the biomedical and ecological (biofouling) viewpoints. The format for this review is identical to that of its immediate predecessor. The review does not provide a comprehensive coverage of all research involving chemicals from marine organisms but concentrates on reports of novel marine natural products with interesting biological and pharmaceutical properties. Biochemical studies involving marine organisms, studies of the biosynthesis of marine natural products, and reports of primary metabolites are specifically omitted. Wherever possible, the biological and pharmacological properties of new marine natural products have been reported but papers detailing pharmacological studies are considered to be beyond the scope of this review. In the area of synthetic organic chemistry, the review focuses on reports of the total synthesis of marine natural products that confirm or redefine chemical structures. No attempt has been made to review the patent literature or conference abstracts, although recent experience has shown that these sources are probably the most important for those seeking new structures for synthesis.