Some speleothems (cave-deposited travertine formations) from two caves in West Virginia were formed in isotopic equilibrium with seepage waters during the interval 200,000 B.P. to the present. Deuterium/hydrogen ratios in fluid inclusions from these speleothems indicate that δ18O values of waters from which they were deposited did not change appreciably during at least part of that interval. From these and other data, we infer that δ18O of calcite increased with decreasing temperature of deposition. Deposition rates appear to be greatest during summer and may have fallen to zero during glacial advances. Curves of relative paleotemperature, based on secular changes in δ18O of calcite as dated by the 230Th/234U method, are presented. Maxima in this record correspond to maxima in summer insolation in the Northern Hemisphere as calculated by Vernekar, as well as to high sea stands marked by raised coral reefs and to thermal maxima observed in speleothems from other regions of North America.