Small Specimen Testing Technology (SSTT) and related remote-control testing techniques are indispensable for the effective use of the limited volumes of material testing reactors and proposed intense neutron sources. As a part of this work, a new fatigue test machine with a laser extensometer for hot-cell usage has been developed. Materials used in this work were Japanese reduced activation ferritic/martensitic steel, JLF-1 (Fe-9Cr-2W-V-Ta) and its weldment. Correlations between fatigue life characteristics and fracture mechanisms were investigated for full- and mini-sized hourglass type specimens to clarify the effect of specimen size on fatigue properties. These tests revealed that there was not significant difference in the number of cycles to failure in both specimens.