The bromination of chiral crystalline sam ples of 4,4'-dimethylchalcone was reinvestigated. In the presence of the optically active reaction product, (+)-or (-)-chalcone dibromide, crystallization from solutions of the achiral chalcone is specifically directed toward one-handedness. A feedback mechanism can thus be envisaged where optically active compounds are formed, generate additional material of the same chirality, and communicate this chirality to other regions, simply by cycles of solidification, reaction, and liquefaction.