Grains of hexaploid wheat, Triticum aestivum (cv. Recital), were collected at 15 stages of development, from anthesis to physiological maturity, 0-700 degrees C days (degree days after anthesis). Two hundred and seven proteins of grain peripheral layers (inner pericarp, hyaline, testa and aleurone layer) were identified by 2-DE, MALDI-TOF MS and data mining, then were classified in 16 different functional categories. Study of the protein expression over time allowed identification of five main profiles and four distinct phases of development. Composite expression curves indicated that there was a shift from metabolic processes, translation, transcription and ATP interconversion towards storage and defence processes. Protein synthesis, protein turnover, signal transduction, membrane transport and biosynthesis of secondary metabolites were the mediating functions of this shift. A picture of the dynamic processes taking place in peripheral layers during grain development was obtained in this study. It should further help in the construction of proteome reference maps for the developing peripheral layers.