Alkali series and tholeiitic basalts from Ojin, Nintoku, and Suiko Seamounts of the Emperor Seamount chain are very similar in their major and LIL (large-ion lithophile) trace-element chemistry to the alkaline and tholeiitic basalts erupted on the island of Hawaii. They are characterized by high total content of alkalis, high TiO (sub 2) and "FeO" contents, low Al (sub 2) O (sub 3) contents, and low Mg/(Mg + Fe (super 2+) ) relative to mid-ocean ridge basalts (MORBs). LIL element abundances in one tholeiite from Ojin Seamount are enriched by factors of 5 to 10 relative to MORBs. REE (rare-earth element) patterns in all the samples are highly fractionated; the heavy rare-earth elements (HREE) are depleted markedly. This is consistent with residual garnet in the source regions. LIL element variations among the seamount basalts suggest variable degrees of partial melting. Olivine fractionation, presumably in a shallow magma chamber, accounts for some of the intra-site major-element compositional variations. There are no systematic differences between the seamount basalts and those from the island of Hawaii that might be attributed to the temporal evolution of a single hot-spot source.