The U.S. seafood processing industry is highly diverse in terms of products and dispersed in terms of geographic location extending from Alaska to Maine. This report was concerned with the impact of effluent guidelines on processors of fish meal, salmon, bottom fish, clams, oysters, sardines, scallops, herring and abalone. The seafood industry studied is characterized by a large number of small plants, decreases in the number of plants over time and important competition from foreign producers. Economies of scale exist, both in processing and in effluent treatment. Opportunities to pass through increased costs due to pollution control to the consumer are limited. Impacts, in terms of plant closures, will be greatest in the Alaskan salmon industry, non-mechanized bottom fish processing, non-mechanized clam processing and the West Coast oyster industry. Out of a total of 381 plants above cut-off levels, it is estimated that BPT guidelines would close 42 plants and BAT guidelines would close an additional 86 plants.