New chemical analyses of rocks from the Troodos ophiolite complex offer no clear evidence that it is a piece of oceanic crust. Ratios of selected nonlabile elements (REE, Zr, Ti) in Troodos lavas clearly distinguish them from the calc-alkaline lavas of evolved island arcs and the oceanic island basalts of Hawaiian and Icelandic type. However, these ratios are equivocal in assigning Troodos lavas to either oceanic ridge, small ocean basin, or young island arc magma series. Gabbros and quartz diorites from the Troodos plutonic complex appear to be derived by low-pressure crystal settling from magmas with the same REE pattern as the overlying lavas and dike rocks. The acidic plutonic rocks have large negative Eu anomalies that clearly distinguish them from silicifed lavas in the complex, which have only small Eu anomalies. Harzburgite, the lowest plutonic unit, has a very low REE content and probably is residual mantle from which the basalt fraction has been removed.