An earlier phytochemical survey of the flavonoid content of heartwoods and barks of Acacia species is extended to a much wider range distributed throughout the Australian continent, and representing most sections and subsections of the genus. Flavonoids with pyrogallol (7,8-hydroxy) A-ring nuclei almost exclusively populate the heartwoods of most species constituting subsections of the Plurinerves and Juliflorae, while resorcinol (7-hydroxy) A-ring analogues are similarly represented under the Brunioideae, Uninerves-subsection Racemosae and the Botryocephaleae. Individual representation of both hydroxylation patterns, or their mixtures in heartwoods. are present amongst the Continuae. and under many subsections of the Pungentes, Calamiformes and Uninerves. A small group. A. prucr(Continuae), A. carnei (Pungentes)and A. crortrbei (Uninerves) show close chemical relationships, being sharply differentiated by the peltogynoid content of their purple heartwoods. This renders them unique amongst the Mimosaceae. Evolutionary trends amongst taxa are discussed on the basis of morphological and chemical correlations.