High cycle fatigue tests were performed on two strength categories (700 MPa and 960 MPa) of high strength steels, on quenched and tempered (Q+T) and on thermomechanical (TM) types, on base materials and their welded joints, as well as on different mismatch conditions (matching (M), undermatching (UM), overmatching (OM), and matching/overmatching (M/OM)). Specimens cut and in full machined from base materials and welded joints, furthermore cut from welded joints were tested. Measured and analyzed data were compared and discussed. Statistical approach was applied during the evaluation of the experiments, which have been allowed for the expansion of the results and increasing their reliability. The parameters of the high cycle fatigue strength or design curves were calculated based on the Japanese (JSME) testing and evaluating method, which uses basically 14 specimens. The article presents and evaluates our results, comparing with each other and with literary data.