1. A radiation image read-out method in which, prior to final read-out wherein a stimulable phosphor sheet carrying a radiation image of an object stored thereon is exposed to stimulating rays which cause the stimulable phosphor sheet to emit light in proportion to the stored radiation energy, the emitted light is photoelectrically detected to obtain an electric image signal for reproducing a visible image, preliminary read-out for approximately detecting the radiation image stored on the stimulable phosphor sheet is conducted by use of stimulating rays of a level lower than the level of stimulating rays of a level lower than the level of stimulating rays used in the final read-out, read-out conditions in the final read-out and/or image processing conditions are adjusted on the basis of the information obtained by the preliminary read-out, and the final read-out is carried out by use of the adjusted conditions, wherein the improvement comprises the steps of: (i) creating a histogram of preliminary read-out image signals obtained by said preliminary read-out, (ii) determining the presence of a sharp peak region arising in the vicinity of at least one of the maximum signal value and the minimum signal value in said histogram, (iii) calculating a characteristic value of said preliminary read-out image signals within a region at least outside of the sharp peak region arising in the vicinity of the maximum signal value and/or the minimum signal value in said histogram, and (iv) adjusting said read-out conditions in the final read-out and/or said image processing conditions on the basis of said characteristic value.