As part of a joint research project, pile load tests applying various static and dynamic testing methods were performed on slender driven piles, i.e. prefabricated driven cast-iron piles (ductile piles). The tests, carried out in clayey soil at a test site in Austria, comprised conventional static compression and static tension load tests, bi-directional load tests with the Pile HAY-Proof-System® and dynamic load tests using the CAPWAP approach. In the scope of this paper the results of the pile load tests are presented and the bearing behaviour of slender driven piles in clay is discussed in the light of the various testing methods applied.