Tree ring ΔD records do not always reflect variations in the average annual ΔD values of local precipitation, but may instead record changes in the ΔD values of seasonal components of precipitation. The ΔD values measured for tree ring sequences from the three trees in this study are correlated with variations in summer climatic conditions at each of the sites. The D/H ratios in an aspen from Fairbanks, Alaska, correlate with summer temperatures in Fairbanks. An aspen which grew near Anchorage, Alaska, and a pine located near Seeley Lake, British Columbia, contain ΔD records which correlate with the amount of summer precipitation at their respective sites. The ΔD variations of the two Alaskan aspens are correlated for the five 5-year sample intervals which they have in common. It is emphasized that a correlation between tree ring ΔD variations and a local seasonal climatic parameter for a given tree does not imply that all trees in that area will exhibit similar correlations. The site and growth conditions of individual trees will probably determine what climatic signal is contained in the D/H records of eac