The paper presents the results of a project aimed at investigating fatigue behaviour of different asphalt mixes using the indirect tensile test (ITT). A standardized criterion for all asphalt mixes is required to determine the fatigue curves with regard to micro crack and macro crack formation. Based on the concept of dissipated energy a method for ascertaining the number of load cycles required up to micro crack and macro crack formation will be presented in the paper. The investigations proved that the set up of strain-dependent fatigue curves as being reasonable. Furtermore it will be demonstrated that the empirical approach to describe the fatigue behaviour of asphalt using ITT results and the rheological model of the fatigue behaviour of asphalt using fractional reological bodys are based on the same mathematical functions. The analysis of the test results showed that an increase in fatigue strength might be expected when using polymer-modified asphalts. Thus the ITT also represents an adequate test method for the determination of input values for the analytical design of flexible pavements with respect to fatigue behaviour. Nonetheless, the number of load cycles to fatigue failure expected in situ in the pavement can not be estimated directly on the basis of the results of the dynamic ITT.