In this investigation the fracture of normal and high strength concrete under monotonic and cyclic tensile loading was studied in order to describe its softening behaviour on the basis of fracture mechanical conceptions. A series of deformation controlled uniaxial tensile tests on notched and unnotched concrete prisms was carried out. The main parameters in the experiments were the number of cycles to failure, the deformation rate, the concrete grade and the curing conditions. Additionally, the fracture surfaces were studied using projected fringes technique in order to gain a more detailed glance on the formation and propagation of cracks under tensile loading conditions. The experimental results show in particular that with an increasing number of load cycles the uniaxial tensile strength decreases. Further, for an increasing number of load cycles the corresponding envelope curves differ significantly from the monotonic curve. This clearly shows that the conventional assumption of a unique envelope curve for the fatigue behaviour of concrete is admissible only for a low-cycle fatigue loading, but cannot be maintained for the high-cycle fatigue.