Thermal barrier coatings are used for temperature reduction of hot parts (combustor and turbine) in both aeroengines and land-based gas turbines. During repeated thermal loading cracks will initiate and grow both in the ceramic topcoat and at the interface between top- and bondcoat. In order to use coatings properly it is essential to understand the mechanisms controlling degradation processes. In the present paper results from thermal cyclic loading of thermal barrier coatings are presented. Testing is done according to thermal loads in stationary turbines for power generation. The coating system used in the present work is a vacuum plasma-sprayed thin thermal barrier coating. As topcoat yttria partially stabilised zirconia has been used and as bondcoat a NiCrAlSiY-type composition was chosen. In the present study, the life-determining mechanism for TBC spallation was found to be formation of interface-near cracks. Cracks growth mechanisms are discussed and delamination crack growth data is presented.