Neutron streaming through the holes penetrating the grid-plate shield of a prototype liquid-metal fast breeder reactor was experimentally examined. The mockups of the grid-plate shield were made of iron and aluminum. Experiments were conducted in the vertical column of YAYOI, the fast-neutron source reactor at the University of Tokyo. A 3He spectrometer was employed to measure the transmitted neutron spectrum, while rhodium and indium threshold foils were used to determine the integral flux above specific energies and their spatial distributions in the form of reaction rates. The streaming factor for usual small bent holes is 1.28 ± 0.04 for the integral neutron flux above 0.1 MeV and 1.30 ± 0.12 for the reaction rate of the indium foil. Use was made of the one- and two-dimensional neutron transport codes ANISN and TWOTRAN for evaluation by computation. The reaction rates calculated by an infinite slab model with the ANISN code agree well with the experiments when normalized at the source point where neutrons are incident on the grid-plate shield.