To investigate the role of the circadian clock of the photoreceptor cells in regulation of retinal protein rhythms, we have analyzed diurnal protein expression in the photoreceptor-deficient cone-rod homeobox knock out mouse (Crx-/-). Retinal homogenates of 129/sv and Crx-/- mice were analysed by 2D-PAGE. Differentially expressed spots were in-gel digested with trypsin and identified by LC-MS/MS. Data were used to search the Swiss-Prot protein database.