Microstructural examinations have been performed on irradiation-creep and thermal-creep pressurized tube specimens of V-3Fe-4Ti-0.1Si in order to understand failure and creep mechanisms. There are no typical microstructural differences between unstressed and pressurized creep tube specimens irradiated in ATR-A1 in the irradiation temperature regime from 212 to 300 degrees C. Failed thermal creep specimens show dislocation structures dependent on the tube specimen geometry. This can be interpreted in terms of a large number of slip dislocations oriented for optimum slip. (c) 2005 Elsevier B.V. All rights reserved.