Seismic reflection profiles show that the principal guyots in the Emperor Seamounts as far north as lat 45° 30′ are capped by ancient coral reefs. Ocean temperatures during the Cenozoic were probably not warm enough to permit reef growth at the present latitudes of even the southernmost of the Emperor volcanoes investigated. The results of our study indicate northward movement of the Emperor Seamounts as predicted by the hot-spot hypothesis.