The fatigue behavior of concrete is mostly studied on the basis of constant amplitude tests. Constant maximum and minimum stresses are applied to concrete specimens during these tests. Usually the applied loading frequencies are between 1 Hz and 10 Hz. To minimize the test duration it is often attempted to increase the loading frequency. However, the loading frequency seems to have a strong influence on the number of load cycles to failure which should not be neglected. Based on results of fatigue tests documented in literature, this contribution shows that the influence of the loading frequency on the fatigue strength of concrete depends on the concrete temperature during the tests as well as on the loading rate. Own investigations on a high-strength concrete confirm this observation. This knowledge should be taken into account by planning fatigue tests or analysing fatigue test data of concrete.