Effects of experimental conditions (such as microwave power, modulation amplitude, ESR cavity temperature, detector phase and thermal pretreatment) on the ESR spectra are studied. Following conclusions can be deduced from this study: 1. (1) Radiation-induced lines, h1 ( g = 2.0057), h2 ( g = 2.0021), h3 ( g = 2.0008) and B.L. ( g ≈ 2.004) are saturated with microwave powers of 5–40, 10, 80–200, 0.5 mW respectively (depending on the ESR cavity temperature). 2. (2) Paleodoses deduced from h1 (after thermal pretreatment) are not quite dependent on the microwave power. 3. (3) All these lines disappear with a detector phase shift of 90°. 4. (4) h1 and h3 are no more detectable at temperatures less than 223°K and 193°K respectively. This diasappearance is likely related to molecular rotations of these centers. Characteristics of h2 and B.L. lines are therefore studied at 193°K without influence of h1 and h3 lines. 5. (5) The spectral forms of individual lines are obtained from the comparison of spectra measured under different conditions. 6. (6) Line narrowings upon thermal pretreatment are observed. 7. (7) Good agreements between the ED values obtained from h1, h3, and B.L. lines on 100 kyr calcite YL1 of Lazaret cave and between the ED values obtained from h1 and B.L. lines for three > 300 kyr calcites of Arago and Petralona caves show the non foundation of the hypotheses supposed in the criticisms on the use of h1 line for the Palaeolithic calcite dating.