This chapter discusses the composition of the surface film and specific surface processes primarily by giving examples of relevant references, rather than trying to list extensively all reports. The surface concentrations and E values will, of course, increase dramatically if the concentrations are corrected for a surface microlayer as calculated by Sieburth et al. Oceanic samples with low bulk concentrations generally showed higher E values. The structure of the surface film and associated surface microlayers has been modeled based upon the presence of chemical components and the biotic and abiotic particulate matter that has been recovered there. In this review, the surface microlayer and all additional surface strata will be referred to as the surface film. Differences in surface microlayer composition between various aquatic ecosystems will depend upon differences insources of film material, rate of transport of material to and from the interface, and possible transformations within the microlayer.