The distribution of mercury in surface sediment from four estuaries along the Khuzestan shore, north part of Persian Gulf, was measured. The concentration of mercury varied among sampling stations (p < 0.05). The concentrations of mercury in all estuaries were from 0.01 to 2.16 µg g(-1). Relatively high mercury concentrations were observed in sediments from Musa estuary. The percentage of mercury associated with different fractions in the sediment from all stations were in the order of residual (70.4 %) > organic matter (16.6 %) > easily and exchangeable (2.2 %) > acid reduction (0.8 %). I geo values calculated for mercury (1.5) showed higher values in Musa estuary than in the other stations. The bioavailability of mercury in sediments could be controlled by physicochemical factors such as pH, oxidation and reduction potential, organic carbon content and cation exchange capacity.