This Report is a review of the literature of marine natural product chemistry that was received in La Jolla during the period 1 September 1986 to 1 December 1987. This is the fifth in a series of reviews published in Natural Product Reports. The earlier cover the period from 1977 to September 1987. A review entitled 'Recent Developments in the Field of Marine Natural Products with Emphasis on Biologically Active Compounds ' has provided an excellent coverage of the field by including over 1000 structures and 160 references. More detailed reviews of 'The Structure of Palytoxin' and 'Sesterterpenes: an Emerging Group of Metabolites from Marine and Terrestrial Organisms' have also appeared. Although the research effort devoted to the structural elucidation of marine natural products has remained almost constant, there has been a considerable expansion of research in areas that are directly influenced by marine natural product chemistry. Much of the peripheral literature has been difficult to track and some papers have been judged to be beyond the scope of this review. In general, only papers pertaining directly to specific marine natural products will be included. In the area of synthetic organic chemistry, reports of the total synthesis of marine natural products are included but papers dealing with methodology that is directed toward the synthesis of a marine metabolite are omitted. Studies of the chemical ecology of marine organisms are included only if research was performed using pure compounds. Pharmacological studies using marine natural products are rapidly increasing in number and scope. While every effort will be made to record the pharmacological activity of new metabolites, studies of mechanisms of action and reports of basic pharmacology in which marine natural products were used as biochemical probes will be reviewed only when they report a significant change in the biomedical status of a compound. The patent literature will not be reviewed in detail, due to its relative inaccessibility, but it is known that an increasing number of marine natural products have been patented as potential pharmaceuticals and, in one case, as a potential sunscreen. Chemotaxonomic studies will be reported when they result in a significant revision of the systematic status of organisms.