The Japanese oyster Crassostrea gigas is commercially grown in bays and estuaries of the Pacific Northwest. The oyster's complex, ciliated, plicate gill is responsible for removing particles from surrounding waters for ingestion. In order to determine how this is accomplished, structural interrelationships of gill components were investigated using scanning electron microscopy and light microscopy. Particle movement was observed directly on both isolated gill sections and intact gills. Feeding data were obtained by comparing initial to final concentration and size of algal particles in a Coulter counter.