An autoradiographic process for obtaining locational information on two or more radioactively labeled substances which have different energy or half-life and are contained in a sample such as tissue of an organism. Specifically, the process includes the steps of placing the sample on a stimulable phosphor sheet having a plastic cover layer to cause the stimulable phosphor to absorb radiation energy of the labeled substances and reading the absorbed radiation energy out of the phosphor to obtain an image signal corresponding to one radioactively labeled substance and placing the sample on a stimulable phosphor sheet having a thinner plastic cover layer or no cover film to cause the stimulable phosphor to absorb radiation energy of the labeled substances and reading the absorbed radiation energy out of the phosphor to obtain image signals corresponding to plural radioactively labeled substances. Then, the process includes the step of subjecting the image signals of (a) and (b) to subtraction processing so that image signals corresponding to plural radioactively labeled substances can be separately obtained.