Foulmg organisms at twelve different pearl oyster beds in the Qatari waters of the Arabian Gulf have been examined and their degree of abundance was assessed. The majority of fouling organisms were algae, sponges, bryozoans* polychaetes, crustaceans, gastropods, bivalves, amphineurans, stelleroida, actinozoans, hydrozoans and ascidians. The list of fouling species identified included a total of 111 species. The highest number recorded of fouling species was at Akraiyash site with the highest diversity index, while the least number was reported in Um Al-Cheteb with the lowest diversity index.