High-resolution high frame-rate neutron radiography system was developed. To achieve the high resolution, various combinations of imaging devices such as a fluorescent converter, high-speed video camera, and image intensifier were tested. Gen III image intensifier (GaAsP) combined with high-resolution high-speed video camera produced good-quality images. By using the new imaging system, measurement error of instantaneous void fraction and decay characteristics of fluorescent converter were estimated. In addition, the imaging system was applied to 3-D measurement of spherical particle position, which enables to measure 3-D velocity field combined with Particle Tracking Velocimetry. (c) 2005 Published by Elsevier B.V.