This review covers the literature on marine natural products published in 2002. As in previous years there has been enormous interest in the structure elucidation, synthesis, activity and ecology of marine natural products. Marine sources produce compounds of new structural types with an intriguing array of biological activities. Sponges are the commonest organisms to be studied, however, algae, bacteria and fungi have been far from neglected. The bioactivity-guided extraction and purification of crude extracts has produced highly potent compounds. Marine species have been interacting chemically for billions of years and it is no wonder that there have evolved natural products with such high activity. Some are highly toxic whereas others have very selective activities and have the potential to be used therapeutically.