Abstract Fish protein concentrates (FPC's) have been used in various parts of the world for several centuries. It has only been within the past 30 years, however, that the production of FPC has been investigated on a scientific basis. Today several pilot plants and full scale industrial plants have been built. Some are now in operation and others will be within a matter of months. Most of these plants produce FPC by solvent (usually isopropylalcohol)extraction procedures. The FPC's produced are, in general, bland tasting and vary in color from white to dark tan. They contain between 75 and 95 percent high-quality protein and they exhibit limited functional properties according to standards set by industry for high protein foodstuffs. The characteristic of limited functional properties, far from being a drawback, is in many circumstances advantageous since FPC can be added to existing food products to markedly improve the nutritional quality without significantly altering other characteristics. Also in some instances, the addition of FPC appears to improve the shelf life of final baked products. One must not assume, however, that all solvent extracted FPC's nor even all isopropyl alcohol extracted FPC's, are completely alike. On the contrary, significant differences in odor, lipid content, stability, taste, nutritional value, and functional properties are obtained depending upon the processing conditions and the species 0f fish used. Experimental work is now being conducted to produce FPC with various solvents, with enzymes, microorganisms, or combinations of enzymes and, solvent. The functional properties of products resulting from these processes are improved. Some of these products appear to be particularly promising for use in certain foods because of their functional attributes. Although many problems still remain to be solved and additional research is required to show how FPC can be utilized more efficiently, an FPC industry has been born and is growing. Introduction Fish protein concentrates (FPC's) are defined as those products obtained from fish in which the protein is more concentrated than in the original raw material. FPC's may range from colored, bland powders to dark powders having intensely fishy tastes, or they may be pastes with a similar wide range of colors and tastes. Both powders and pastes may be water soluble or insoluble and may be high in nutritive value or only intermediate in nutritive value. FPC's may be prepared by a variety of methods most of which can be classified as chemical (solvent extraction) or biological (enzymatic and microbial) procedures. During the last 20 years most efforts have involved the use of solvents, usually isopropyl alcohol, and several pilot plants and a few full-scale industrial plants have been constructed. Some of these plants are now in operation and others will be in a matter of months. The type of FPC produced by solvent extraction is bland, nearly odorless, lightly-colored, water-insoluble but highly nutritive powder, intended for use as a protein supplement.