ABSTRACTThe fibrous protein paramyosin is characteristic of invertebrate muscles. It is distributed in the phyla Platyhelminthes, Nematoda, Nematomorpha, Annelida, Mollusca, Arthropoda and Echinodermata. Of these, the last three contain important edible seafood species. The molecular weights, amino acid profile and immunological features of the paramyosins isolated from many invertebrate phyla are surveyed comparatively. In addition, the paramyosin literature reported predominantly from the investigations on bivalve molluscs(Mercenaria and Mytilusspecies) is reviewed under categories (1) microstructure, (2) solubility and stability characteristics, (3) phosphorylation, and (4) involvement in catch contraction. The importance of paramyosin to the quality of seafood systems has not been studied in detail so far.