Thermorheological behaviour and dilatometric glass-transition temperatures have been studied on 14 samples representing the three main types of bitumen. The frequency dependence of the dynamic moduli can be described byGaussian distributions of log relaxation time. The width of the distribution depends on the type of bitumen. The frequency-temperature shifts or the viscosity-temperature relations correspond with free-volume equations for temperatures not too close to the thermodynamic glass-transition temperatures. The constants in the free-volume equations vary with the type of bitumen. The dilatometric glass-transition temperatures do not serve as simple references for corresponding free volume states. Their significance was found to depend on the type of bitumen. In this respect it is noteworthy that the dilatometric glass-transition temperatures approach the thermodynamic ones as the spectra become narrower.