Chemical and physical measurements were made on soil samples and leaf material from Acacia georginae in order to investigate a number of factors which were considered to be possibly influencing the uptake of fluoride by the plant in the field. No correlation was found between leaf fluorine levels and any of the factors measured. The available evidence suggests that the 100-fold variation in leaf fluorine levels found is not due to variation in soil composition; this conclusion was supported by pot trials using soil from trees with high and low leaf fluorine levels. High leaf fluorine levels (> 10 p.p.m. of air dry material) were found in the field only where the tree grows over carbonate bedrock (limestone or dolomite); however, only a small percentage of the trees in such areas have elevated leaf fluorine levels.