Monthly samples of the bivalve Pinctada fucata were collected within one year (1995-96) in the north-eastern (Nakhiloo, Hendurabi and Lavan) of the Persian Gulf. The objective of this study was hydrocarbons quality survey. Thy above regions are natural habitant of pearl oyster (P.fucata). The primary sampling showed that pearl oyster stocks decreased in Lavan and Hendurabi regions, therefore the regions were selected as experimental stations. The oil hydrocarbons were measured in water (surface and depth), sediment and bivalves. The result indicated that in the north of Lavan, due to few currents of water hydrocarbons' concentration was more than north eastern part of Lavan, Hendurabi and Nakhiloo regions and in the, Nakhiloo region, in which hydrocarbons were less than studied stations, the bivalve size were larger.....