The effects of particles on the linear stability of an oscillatory two‐phase plane channel flow are examined for small Stokes numbers. The results in this note are valid for the condition that the dimensionless oscillation frequency is of the order of unity or smaller. The particles are found to have a destabilizing effect at all flow oscillation frequencies except in the high‐frequency region and the extent of the destabilization increases with increasing particle mass fraction. The critical Reynolds number for a gas–particle flow may be significantly changed by the flow oscillation. ©1995 American Institute of Physics.