Significant seasonal changes in the electrical resistance (ER) of inner bark of tagged lodgepole pine (Pinus contorta Dougl.) trees accompanied corresponding changes in bark moisture content. However, moisture contents on a given day of measurement were not correlated with ER. Significant correlations (0.05 level) were found for ER-phloem thickness, and ER-diameter. Moisture content was not one of the factors requiring measurement and standardization, when using electrical resistance to detect relative differences in vigor among trees of the same stand--when comparisons are made only with measurements of ER taken on the same day. Forest Sci. 26:309-312.