Fieldwork, radiometric (40Ar/39Ar and 14C) ages and whole-rock geochemistry allow a reconstruction of eruptive stages at the active, mainly dacitic, Pichincha Volcanic Complex (PVC), whose eruptions have repeatedly threatened Quito, most recently from 1999 to 2001. After the emplacement of basal lavas dated at ~1100 to 900 ka, the eruptive activity of the old Rucu Pichincha volcano lasted from ~850 ka to ~150 ka before present (BP) and resulted in a 15×20 km-wide edifice, which comprises three main building stages: (1) A lower stratocone (Lower Rucu, ~160 km3 in volume) developed from ~850 to 600 ka; (2) This edifice was capped by a steeper-sided and less voluminous cone (the Upper Rucu, 40–50 km3), the history of which started 450–430 ka a...