The burrowing ophiuroid Amphiura filiformis (O. F. Müller) is a dominant member of a silty sand community in Galway Bay on the west coast of Ireland (53°13′16″N; 9°6′30″W). High-density populations in the area (greater than 700 m-2) generally occur in sediment having a silt/clay content of 10 to 20%. On the basis of such numerical prominence, the species has been under investigation at a fixed monitoring station since 1974. Throughout the study period, adult individuals consistently accounted for ca. 95% of the population; annual recruitment was invariably found to be extremely low. Annual desities showed a declining trend to 1980, following which there was some evidence of a rise in numbers. This situation is assessed in the light of what is currently known of A. filiformis from different geographical locations.