A population of the annual Lasthenia californica in the Jasper Ridge Biological Preserve (of Stanford University) showed three major flavonoid pigment types (A, B and C; a fourth was seen in very low frequencies). The three more common types exhibited a suite of aurone and chalcone glucosides and a set of highly polar flavonoid glucuronides. Type C consisted solely of the base array; type B added luteolin 7-glucoside to the base array, while type A exhibited the base array plus eriodictol 7-glucoside and flavonol 3,7-diglycoside bisulfates. The rare type D profile resembled type A except that the diglycosides were not sulfated. Collections were made along one of several fixed transects annually from 1982 to 1987. The main transect studied (Transect No. I) can be divided into two distinct parts on the basis of a changeover of flavonoid pattern from a mixture of types B and C at one end to exclusively (or very nearly) type A at the other. The frequencies of types B and C varied from year to year with type C predominating every year. The frequency of type A plants remained remarkably stable over the six-year period. Collections along other transects showed a similar constancy of both frequencies of the flavonoid types and location of the types along the transects. Growth experiments in a greenhouse showed that seeds from type A parents harvested in the field produced only type A progeny, while type B and C plants gave only type B and C progeny with type C predominating (a single type A progeny plant was obtained from a type C parent). Flavonoid diversity in L. californica appears to be genetically controlled and is influenced significantly by the flavonoid chemistry of the seed parent.