Total alkali-silica diagram for ten samples from site 803 and eight samples from site 807 of the Ontong Java Plateau indicate that the rocks are typical tholeiitic basalts; however, there are fundamental differences in the major, trace and REE chemistry between the two sites. For example, in the MgO-TiO2 plot, samples from sites 803 and 807 cluster at different parts of the diagram implying different source regions for the magmas of the two sites. In addition, the range of the MgO values for the two sites (6.74 to 4.66 wt% for 803, and 7.29 to 6.56 wt% for site 807) reflect different degrees of differentiation at low pressures. Low Ni values for site 803 (110-86 ppm) and site 807 (99-83 ppm) indicate olivine fractionation, and low Cr values for site 807 (161-171 ppm) indicate clinopyroxene fractionation. Variation of Cr with MgO for site 807 suggests less clinopyroxene fractionation at this site compared to site 807. Additional plots of MgO against other oxides show some scatter reflecting various degrees of hydrothermal alteration of all samples. Trace and REE element data from sites 803 and 807 show that the Ontong Java Plateau samples have Ba, Th, La, and Zr values higher than N-MORB, and Ti, Tb, Dy, Y, and Yb values lower than N-MORB. Our REE data for the samples display slight enrichment of LREE with respect to N-MORB, and depletion with respect to OIB indicating that the source regions of the basalts of the Ontong Java Plateau are different than those of N-MORB and OIB.