Galway Bay is the site of a large natural oyster bed (Ostrea edulis) on the west coast of Ireland which has been infected with the protozoan parasite Bonamia ostreae since 1989. During the Summer and Autumn of 1996 native flat oysters were collected from a number of oyster beds in Galway bay. These were examined for the presence of B. ostreae and intensity of infection was noted. Whole weights of oysters were recorded and indicated that oysters of all weights were infected. Results would indicate that the parasite is still present but at a lower level than when initially diagnosed in 1989. Also, though the prevalence of infection has dropped, the disease has spread within the bay over the past nine years.