We present a high-speed, high-resolution beta imager. It has been developed to be used in in situ hybridization experiments, either instead of or in complement with autoradiographic film and emulsions that are currently used for these experiments. It allows the user to locate and perform quantitative analyses of (3H-, 14C-, 35S-, 32P-, 125I-) labeled molecules with a 15-microns spatial resolution on a 1.2 cm2 area. We have combined recent techniques (specific scintillator thin sheets and intensified charge-coupled device [CCD]) so that this imager offers a wide dynamic range and real-time acquisition. Several biological applications will be discussed.