Abstract A personnel dosemeter for routine dosimetry in mixed beta-gamma fields requires a thin, nearly tissue-equivalent detector with a high sensitivity and with a high mechanical resistance. A special TL sandwich detector has been designed for application in beta dosimetry. It consists of two TL sensitive layers (TLD 1 and TLD 2) separated by a material with poor thermal conductivity. In consequence of the poor thermal conductivity of the separating layer the temperatures of TLD 1 and TLD 2 are different during the evaluation process. The TLD 1 layer shows an excellent beta sensitivity (about 75% for 14C beta rays related to 90Sr/90Y). Information about the radiation field can be obtained by using the relation of the detector readings of TLD 1 and TLD 2. The production of the TL sandwich detector is described, and the dosimetric properties in different beta fields are represented and discussed.