The first objective of this introductory paper is to summarize our present understanding of the quantities of total organic carbon produced in the ocean by photosynthesis and non-biotic photochemical reactions, and the amount entering the ocean from rivers, the atmosphere, and the sediments. In this overview it will become apparent that our knowledge of the primary mechanisms and processes involved with the input of organic matter to the ocean via rivers, the atmosphere, sediments, and in situ photochemical reactions is fragmentary and often completely lacking. This becomes critical when we attempt to estimate the input of certain naturally occurring organic compounds and some synthetic organic compounds, since their primary input to the sea is generally via the atmosphere, rivers, and dumping. Thus the second objective of this paper is to emphasize our need to understand the mechanisms involved in these other input processes and the necessity of developing field programs and mathematical models to evaluate the input of specific organic compounds via these pathways. Polychlorinated biphenyls are used as examples of how necessary it is to understand these other input routes in order to evaluate the cycling of pollutant substances in the ocean.