Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite were measured by an electron probe microanalyzer to study the effects of reduction on the Mn-Fe value, because ureilite olivines exhibit thin reduced rims. The Mn content gradually increases toward the rim of ureilite olivines as the Fa (=100¿Fe/(Mg+Fe), mol %) component decreases, which suggests that the Mn-Fe content of olivine is related to redox conditions. A calculated diffusional cooling rate of 1--2 ¿C/h gives the best fit to both the observed MnO and Fa chemical zoning profiles of ALHA 77257. The results of melting experiments suggest that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction and that the Mn-Fe positive correlation is related to temperature. The Fe/Mn-Fe/Mg trend of olivine cores in ureilites may be established by the reduction process at about 1275 ¿C. ¿ American Geophysical Union 1993