This Report reviews the literature of marine natural products chemistry that was received in La Jolla during the period 15 July 1985 to 1 September 1986. The Report is the fourth of a series of reviews in Natural Product Reports: the first covered the literature published between 1977 and October 1983 concerning metabolites of marine algae and herbivorous marine molluscs, the second reviewed the literature on metabolites of marine invertebrates from 1977 to July 1984, and the third review of marine natural products updated both earlier reviews to July 1985. A few papers that were omitted from the previous reviews have been included in this Report. The reviews of 'Marine Alkaloids and Related Compounds' and 'Marine Alkaloids' have provided excellent coverage of this area of the literature. A review of the total synthesis of marine natural products emphasizes the contribution of synthetic organic chemistry to the development of marine natural products chemistry. Several of the papers that were presented at the IUPAC conference on Marine Natural Products in Paris provided overviews of topics that included 'Chemical Defense in Sponges', 'Pharmacologically Active Substances from Southern Pacific Marine Invertebrates', 'Marine Natural Products: New Results from Mediterranean Invertebrates', and 'Marine Natural Products as Leads to New Pharmaceutical and Agrochemical Agents'. Other papers from the IUPAC conference are reviewed in the appropriate sections below. The level of interest in marine natural products is being maintained at a healthy level and the areas of interest seem to be expanding. The pharmaceutical industry has become more involved with marine natural products, and one can reasonably expect to find products being developed by using leads that have been derived from pharmacological studies of marine natural products. The roles of natural products in the marine environment are just beginning to be understood. Although the major thrust of studies of chemical ecology in the marine environment has been to elucidate defensive roles of secondary metabolites, there is an increasing interest in the possibility that secondary metabolites may also act as inducers of settling and as natural anti-fouling.