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This study investigated a methodology for sampling and extracting water from Eucalyptus spp. for analysis of stable isotopes of water. Firstly, water of known isotopie composition was extracted from stems of seedlings of Eucalyptus spp. by azeotropic distillation using three solvents (hexane, toluene and kerosene) in laboratory and glasshouse experiments. Kerosene and toluene gave the most accurate extractions, with a small negative bias (~-2%c for 5^H and ~~0-4%c for 5*^0) due to incomplete extraction. This bias was not evident in further experiments, using kerosene, where water was extracted from stems and roots that had been pre-treated in a manner that more closely reflected field conditions. Secondly, variation in 6^H in trees was investigated in the field to determine an accurate and convenient place for sampling. There was no significant difference in 8^H between water extracted from trunk sapwood and whole twigs, even twigs close to leaves, in samples taken from four Eucalyptus spp. at two field sites. The results mean that the most convenient part of the tree can be sampled. Also, there was little difference in 6^H between sapwood and heartwood samples, although small increases (~ 2%c) in 5^H were observed in bark of trunks and twigs. Tree roots (15-25 mm diameter) had similar 6^H values to the surrounding soil in many cases, especially surface (<0 2 m depth) roots, rather than having 5^H values similar to twigs of the trees. These roots were absorbing water from surrounding soil, but not contributing significant quantities of water to the tree canopy. Thus, the 6^H of root water is not a good indicator of the isotopie composition of water in the upper parts of Eucalyptus trees.

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