Between 1971 and 1978 up to 64% of commercial-sized saucer scallops, Amusium balloti, in samples from the landed catch at Shark Bay were infected with the larval ascaridoid nematode Sulcascaris sulcata. The presence of the nematodes and the brownish capsule in which they were found made some of the processed catch unsuitable for export. A small percentage of the scallops also contained a larval gnathostome, Echinocephalus sp. Five of six loggerhead turtles, Caretta caretta, from the same area were found to contain adult S. sulcata. Also present in the turtles were the cucullanid Cucullanus cauettae, the oxyuroid Kathlania leptura and the larval gnathostome Echinocephalus sp. Four of the turtles had been feeding chiefly on bivalves, one on crabs, and one on gastropods. Ulcers, probably associated with S. sulcata infection, occurred in the stomach, and small haemorrhages, probably associated with the feeding sites of C. carettae, occurred in the intestine.