Epifouling assemblages. on pearl oyster shells in onshore and offshore'oyster beds, at Qatari water, Arabian Gul£ were investigated in relation to oyster size and flesh growth. Onshore oysters had great biofoulers and low growth parameters than offshore ones. In both beds, biofoulers were dominated by sponges, thorny oysters, polychaetes and red algae. Of these, the serpulid worm (Serpula vermicularis) and the thorny oyster (Spondylus marisrubri) were the most pronounced particularly in onshore oysters. Density of biofouler settlement increased with shell surface areas. Most biofoulers tended to settle on dorsal side of the pearl oyster except the tube worms which preferred the ventral side.