Our current research program focuses on the investigation of marine natural products with potential use as human therapeutic agents, as biological probes or as lead structures for medicinal chemistry. Our primary emphasis is on the discovery of compounds with anticancer properties, but we are also involved in collaborative research programs aimed at the discovery of agents useful against neurodegenerative disease and infectious diseases such as malaria and tuberculosis. Natural products are obtained from marine plants, invertebrates and microorganisms isolated from the tissues of marine invertebrates. Much of our work has focused on the investigation of deep-water organisms collected using the Johnson-Sea-Link submersibles. Over the past few years we have actively built a library of enriched fractions -- the Harbor Branch Peak Library -- that is available for screening in new assays through collaborative agreements. Bioassay-directed fractionation is used to purify the bioactive materials, and the structures of new compounds are determined through spectroscopic means with an emphasis on the use of nuclear magnetic resonance spectroscopy. Our research program has an increasing emphasis in defining the mechanism of action of the compounds using methods such as small molecule immunochemical (affinity) chromatography.