Morphologic and magnetic data suggest that the Mid-Pacific Mountains formed during Early Cretaceous time as a broad ENE trending double chain of midplate island seamounts over a mantle hot spot as the Pacific plate moved westward and slightly southward. Dredge, drill core, and reflection seismic data indicate that coral-rudistid reefs grew on the subsiding seamounts are evolved to atolls and banks, largely burying the volvanic foundations. Magnetic data indicate that by late Aptian time, about 110 Ma, the seamounts were located at about 20¿-25¿S, which we suggest was near the fringes of the latitudinal zone of vigorous reef growth, where upward growth rates could just keep up with subsidence. A broad uplift probbly related to the widespread regional emplacement of Aptian volcanics as oceanic plateaus, seamounts, and deep-water flows and sills raised the Mid-Pacific Mountain reefs out of the water, and both reflection seismic and isotopic data suggest that a karstic topography developed on many of the emergent reefs. As subsidence recommended, the reefs could not grow upward apace with subsidence. Renewed volcanism in Late Cretaceous time in the easternmost Mid-Pacific Mountains maintained islands for a while, as at Horizon Guyot, but probably without large reefs. Elsewhere, pelagic conditions have prevailed as the guyots sank to their present-day depths. These depths are systematically related to the inferred age of the volcanic foundations, being greatest on the youngest volcanoes.