Chemical zoning profiles of olivines in the Esquel, Imilac, and Yamato 8451 pallasites were measured by using an electron probe microanalyzer in order to study their cooling histories. Pallasite olivines are considered to be compositionally uniform but show faint zoning for Fe-Mg, CaO, Al2O3, Cr2O3, and MnO within a few hundred micrometers from the rim. The CaO, Al2O3, and Cr2O3 contents of olivines in pallasites decrease gradually toward the rim. The Fe-Mg zoning and the MnO enrichment in olivine rims of pallasite olivines may reflect a redox process. On the basis of diffusion calculations to estimate the cooling rate by using chemical zoning of pallasite olivine, the formation process of chemical zoning was discussed. Similar cooling rates obtained for the Fe-Mg, CaO, and MnO profiles of an olivine imply that these zoning patterns formed during the same event.¿ 1997 American Geophysical Union