The patterns of oil. sediment rejection of 19 Caribbean hermatypic corals are identical to their patterns of rejection of clean sediments. The rejection pattern is typical for coral species and displays maximum and minimum rates dependent on the size and density of the oil-sediment particles. The viscosity of the oil determines the size of the oil-sediment particles. A coral's efficiency of rejection of sediment depends on the size and amount of the sediment particles. Oil drops 0.06 mm are removed by the coral's tissues. Physical contact with oil-sediment particles appears to be less harmful to corals than the toxic effects of oils.