The Cerro Toledo Rhyolite is a group of high-silica rhyolite domes and tephras that range in age from 1.45 to 1.12 Ma. The unit crops out in the Jemez Mountains of northern New Mexico and lies stratigraphically between the compositionally zoned upper and lower members of the Bandelier Tuff. The Cerro Toledo Rhyolite provides an exceptional opportunity to study the origin of compositional zonation in silicic magma chambers because it allows us to follow the restoration of the zonation with time between these two large caldera-forming ignimbrite eruptions. Based upon stratigraphic, geochronologic, and geochemical evidence, we have correlated different Cerro Toledo Rhyolite tephra units with groups of domes. Early Cerro Toledo Rhyolite domes appear to be located generally along the Toledo caldera ring fracture, whereas younger domes tend to cluster in the Toledo embayment. The Cerro Toledo Rhyolite appears to have tapped the most fractionated liquids at or near the top of the Bandelier magma chamber and records the restoration of compositional gradients over a period of 0.33 m.y. after the Lower Bandelier ignimbrite eruption. Cl, Rb, Cs, heavy rare earth elements, Y, Nb, Th, and U increase in concentration in progressively younger Cerro Toledo Rhyolite rocks. Because of depletions in K/Cs, Sr, Zr/Nb, and La/Yb over the same interval, we favor crystal fractionation of essentially quartz, alkali feldspar, zircon, and a light rare earth element enriched phase (probably allanite) as the primary mechanism by which the compositional gradients were reestablished. We believe diffusive processes did not play an important role because (1) certain cations of widely different valencies and diffusivities are not fractionated with respect to each other and (2) the observed chemical gradients conflict with those predicted by recent experimental Soret studies. ¿ American Geophysical Union 1988