The publication describes the production, properties and main applications of the three major phyco-colloids extracted from seaweed: agar, alginate and carrageenan. There is also a supplementary chapter on the preparation and marketing of seaweeds as food. Although this is based mainly as Japanese experience it is included in order to encourage increased consumption of seaweeds as human food. The authors of the three phyco-colloid chapters have considered raw material sources, post-harvest tr eatment, methods of extraction, chemical composition of the colloids, evaluation of quality, and uses, with some details of economics and marketing.