The influence of the Emperor Seamount Chain upon the mesoscale thermohaline structure and upon geopotential height are investigated on the basis of a field experiment in the summer of 1982. The seamounts have a twofold effect; they deflect the oncoming flow of the Kuroshio Extension, and they give rise to secondary perturbations of small horizontal extent but of large vertical amplitude. The Kuroshio Extension approached the seamounts on a southeastward course and was deflected by Kinmei Seamount in an anticyclonic loop. The deflection led to a weakening of this current over this seamount and to reintensification on the downstream side. Uplift of isopycnals near seamount peaks and vertical displacement along seamount flanks were generally observed, but the details varied considerably from one seamount to the next. Uplift occurred over some peaks; on others it was displaced 50--100 km from it. In some instances there was intense downward displacement on the west and upward displacement on the east side; in others was not the case. A Taylor columnlike feature occurred over Suiko Seamount. A very large and asymmetric density dome was found 40 km west of Jingu Seamount, atop which a density front was located, which suggests flow intensification to the left of the seamount. In the main gap between the northern and southern seamounts, prominent wedgelike intrusions or subarctic and Kuroshio-type waters were observed in the upper few hundred meters. The isopycnals in the main gap sloped sharply to the south, indicating a strong eastward baroclinic flow component. The geopotential heights over the Emperor Seamounts indicate strong local perturbations superimposed upon larger-scale slopes. A geopotential low was observed west of the seamounts, and a high was found near the seamount top or to the east of it, indicating anticyclonic flow. In terms of geometric distance, perturbation dynamic heights reached 0.32 m, and maximum sea surface slopes were 5⋅10-6. The slopes produce baroclinic currents up to 0.5 m s-1 around the seamounts.