The present invention concerns a method for the treatment of stimulable phosphors and/or screens for use in diagnosis, in particular medical radiography. The method comprises subjecting the stimulable phosphors and/or screens to an epoxide containing gaseous compound, promptly following their manufacture. By applying the method according to the invention yellowing of the stimulable phosphors and/or screens is prevented in a safe and efficient manner; thereby the disadvantages known as such resulting from such yellowing will not occur.