The scintillation properties and radiation durability of beta-SiAlON:Eu were evaluated under focused microbeam irradiation conditions using 3 MeV protons. In situ observation of scintillation from beta-SiAlON:Eu was monitored using ion-beam-induced luminescence (IBIL) and compared with that from ZnS:Ag scintillators. A comparison of the spectra of IBIL from both scintillators shows that the intensity of IBIL was analogous at different peak wavelengths of 545 nm for P-beta-SiAlON:Eu and 450 nm for ZriS:Ag under the same irradiation conditions. Better radiation hardness towards focused proton microbeam irradiation was observed for the beta-SiAlON:Eu scintillator when continuous measurements by IBIL were used. A decay constant of approximately 1.11 x 10(16), which is two orders of magnitude higher than that for ZnS:Ag, was obtained for the beta-SiAlON:Eu scintillator for focused proton microbeam irradiation. IBIL was also capable of visualizing a previously damaged area of a ZnS:Ag scintillator, which corresponds to the focused beam scanning area of 100 x 100 mu m(2). Meanwhile, the irradiated region was not significantly distinguishable from the nonirradiated region on the beta-SiAlON:Eu scintillator under the same beam fluence. These results suggest that beta-SiAlON:Eu could be an ideal candidate scintillator for convenient ionized particle beam monitoring and a diagnostic tool for focused and intense beam fluence conditions up to 10(16) ions/cm(2).