As a part of a program to develop an electron paramagnetic resonance (EPR) dosimeter suited for clinical use (doses in the cGy range), polycrystalline samples of lithium formate monohydrate (HCO2Li·H 2O), magnesium formate dihydrate (C2H2O 4Mg·2H2O), and calcium formate (C2H 2O4Ca) have been examined. L-Alanine was included for comparison and reference. Samples were irradiated with 60Co ?-rays and 60-220kV X-rays. The dosimeter response was assessed using the peak-to-peak amplitude of the first-derivative EPR spectrum. Dose-response curves for the 60Co ?-irradiated samples were constructed, and the dependences of the response on the photon energy, microwave power, and modulation amplitude were studied. Stability of the irradiation products upon storage (signal fading) was also investigated. Lithium formate monohydrate is by far the best candidate of the tested formates, suitable for measuring doses down to approximately 0.1Gy. Lithium formate monohydrate is more sensitive than alanine by a factor of 5.6-6.8 in the tested photon energy range, it exhibits no zero-dose signal and shows a linear dose response in the dose range from 0.2 to 1000Gy. Its EPR signal was found unchanged in shape and intensity 1 week after irradiation to 10Gy. Various less favorable properties rendered the other formates generally unsuitable, although calcium formate exhibits some interesting EPR dosimetric properties. © 2003 Elsevier Ltd. All rights reserved.