A gas turbine engine rotor blade containment assembly comprises a generally cylindrical, or frustoconical, stiff containment casing (54), a generally cylindrical, or frustoconical, flexible structure (62) arranged within and spaced radially from the stiff containment casing (54) by crushable structures (64, 66) at axially spaced positions on the flexible structure (62). A viscoelastic material (68) is arranged to fill the space (70) between the stiff containment casing (54), the flexible structure (62) and the crushable structures (64, 66). The viscoelastic material (68) provides local stiffening of the blade containment assembly in the region of a fan blade (34) impact and provides energy dissipation by viscoelastic damping of the flexing of the flexible structure (62) and plastic deformation in the crushing of the crushable structures (64, 66).