We investigated the xenon-induced spatial oscillations in boiling-water cooled reactors by the use of a three-dimensional xenon dynamics code FILE-6, which solves the one-group neutron diffusion equation simultaneously with the steady state thermo-hydrodynamics equations and with the iodine-to-xenon equations in the time domain. The stability limit of the first azimuthal mode in terms of the void coefficient of reactivity was found to be in a 500 MWe heavy-water-moderated boiling-light-water-cooled reactor. When the height of the reactor core is larger than 7 m, the first axial mode becomes unstable for a void coefficient of +0.05. It has also been shown that (i) a positive (negative) void coefficient may have a stabilizing (destabilizing) effect on the axial higher modes depending on the inlet subcooling, (ii) the mode coupling between the axially zeroth and the first modes through voids has a stabilizing effect, and (iii) when the first azimuthal mode is oscillating, higher harmonics are excited in some of higher modes through the nonlinear reactivity feedback.