Thermal neutron responses (TNR) of some thermoluminescence dosimeters (TLDs) were investigated for the application to mixed-field dosimetry of thermal neutrons and gamma-rays. The TNR values of Mg 2SiO 4:Tb (MSO-S) and Mg 2SiO 4:Tb + LiF (MSO-LiF) elements were determined to be 3 mGy and 2.9 Gy, respectively, for a thermal neutron fluence of 10 10 n cm -2. These TLD elements were used for measurements of depth-dose distributions in a phantom in a boron neutron capture therapy study. We measured the thermal neutron and gamma-ray doses simultaneously in the phantom by the MSO-S element having a thermal neutron response which was the same as the kerma factor in wet tissue. The combination of MSO-S and MSO-LiF elements was applied for measurements of low intensity thermal neutrons within the phantom in a mixed field of filtered beam neutrons and gamma-rays.