Global water isotope geochemistry during the last glacial maximum (LGM) is simulated with an 8¿¿10¿ atmospheric general circulation model (GCM). The simulation results suggest that the ''spatial'' Δ18O/temperature relationships observed for the present-day and LGM climates are very similar. Furthermore, the temporal Δ18O/temperature relationship is similar to the present-day spatial relationship in regions for which the LGM/present-day temperature change is significant. This helps justify the standard practice of applying the latter to the interpretation of paleodata, despite the possible influence of other factors, such as changes in the evaporative sources of precipitation or in the seasonality of precipitation. The model suggests, for example, that temperature shifts inferred from ice core data may differ from the true shifts by only about 30%. ¿American Geophysical Union 1994