The 11 900 yr BP Waiohau eruptive episode is a moderately sized rhyolitic event of the Tarawera Volcanic Complex. Subdivision of the pyroclastic fall deposits previously mapped as Waiohau Tephra has allowed the chronology of the eruption to be deciphered. At least 15 events (units A-O) with volumes in the range 50 km) poorly preserved in paleosols. Previous volume calculations are considered overestimates because they included tephric loess. Effusive activity represents 3.9 km3, and pyroclastic debris in the northern sector adds another 2.4 km3, but much of the latter is xenolithic. Deposits from the entire Waiohau eruptive episode were derived from a hypersthene (+ minor hornblende) rhyolite magma that lacked compositional (SiO2 = 78 ﾱ 0.2 wt%) and mineralogic gradients. Electron microprobe analyses reveal that phenocrystic phases lack compositional variation. The bulk of the magma also lacked physical gradients (T=780-790ﾰC; log fO2 = c. -15) as determined by Fe-Ti oxide geothermometry. Eastern Dome and the Pokohu lava display lower temperature (