Studies of radiation damage in magnetoplumbite-type LaMgAl11O19 and CeMgAl11O19 are reported. Ion irradiation was conducted on ceramic composites containing a LaMgAl11O19 phase at 500 degrees C with 10MeV Au+ ions and on ceramic composites containing CeMgAl11O19 phase at 800 degrees C with 92MeV Xe+ ions. The radiation response of these similar LnMgAl(11)O(19) (Ln=La and Ce) hexaaluminate magnetoplumbite phases was evaluated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). LaMgAl11O19 was amorphized by 10MeV Au ions with swelling of the structure within an approximate 2m radiation depth from the irradiation surface. CeMgAl11O19 did not amorphize after 92MeV Xe-ion irradiation, but ion track damage contrast is seen in approximately 5m of the irradiated depth. SRIM Monte-Carlo simulations of nuclear displacements correlate with the experimental results.