This review is concerned with variation of flavonoid patterns within species. Many examples of species with invariant flavonoid patterns are known; there are at least as many examples where complex arrays of pigments are known. Eight categories of variation are discussed: 1) qualitatively invariant pigment profiles, 2) quantitative variation, 3) flavonoid races that do not correspond to recognized taxonomic groups, 4) flavonoid races that do correspond to recognized taxonomic groups, 5) flavonoid profile differences between different ploidy levels, 6) differences between organs or between tissues, 7) differences between developmental stages, and 8) environmentally influenced flavonoid profiles. These types of variation seem to occur randomly in the plant kingdom. Members of the same family, or in some cases, the same genus, can display different types of variation. Careful attention to these sources of variation is necessary before flavonoid characters can be used in taxonomic studies.