A survey of 255 species from 57 genera representing all the tribes in the Iridaceae has indicated considerable heterogeneity in the distribution of flavonoids and other phenolics in the leaves. Thus the Iridoideae and Tigrideae can be distinguished from other tribes by the regular presence of mangiferin, whereas the Trimezieae and Sisyrincheae can be separated by the absence of flavonols. Again, the Aristeae and Nivenieae are distinguished by the presence of plumbagin, although this quinone does occur in isolated instances in two other tribes. These two tribes also rarely have glycoflavones, which are otherwise almost universally present. Members of the Watsonieae are separated by the fact that only flavonols are present, while the Ixieae have a number of distinctive flavones, notably tricin, acacetin, 6 hydroxyluteolin and scutellarein derivatives. Isophysis tasmanica, the only taxon of the Isophysidoideae, is unusual in having the biflavonoids, amentoflavone and dihydroamentoflavone, with only traces of glycosylflavones. Anthocyanin patterns in the flowers also vary at the tribal level, with acylated pigments being apparently confined to the Irideae. Syringetin, larycitrin and myricetin 3-galactosides were identified in flowers of Gladiolus tristis (Ixieae), whereas glycoflavones were found to predominate in flowers of Iris species (Irideae). These varying patterns may be helpful in placing uncertain genera into their correct tribes. The phenolic pattern of the family as a whole is heterogeneous and shows only a few chemical links with any neighbouring families.