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The dependence of nuclear temperature upon excitation energy has been experimentally studied with increasing values of excitation energy over the years. At excitation energies per nucleon, E*/A, lower than 6 MeV the temperatures deduced from the kinetic properties of the emitted particles and clusters follow the Fermi gas law : E* = (A/k).T 2. The value of the inverse level density parameter k was found to be in the range 8 to 13[1]. When excitation energies up to 10 MeV per nucleon were reached, temperatures obtained from the relative populations of excited levels in the emitted light nuclei did not overcome 5–6 MeV[2], but this limitation could be explained by side-feeding effects. Such hot nuclei were formed in fusion or deep inelastic reactions. At incident energies above 40–50 MeV/u, binary dissipative collisions dominate and the quasi-projectiles reach excitation energies per nuclEon and kinetic temperatures above 10 MeV[4, 5]. The study of projectile “spectators” in reactions at several hundreds of MeV/u made it possible to reach similar excitation energies[3]. In this Aladin experiment at GSI, the temperature was obtained via the relative abundances of two isotope pairs[6]. The relation between this temperature Tr 0 and E*/A was interpreted as indicating a phase transition, with the nuclear gas regime dominating above E*/A = 10 MeV, as predicted[7]. However, a monotonic increase of the temperature with excitation energy was observed in similar conditions[8] and questions were raised about the significance of these caloric curves[9, 10, 11, 12], about the role played by the mass dependence of the decaying nucleus upon E*/A [13], as well as the strong effects of side-feeding, especially at high temperatures [14]. This point will be discussed by Xi Hong Fei at this meeting.[15].