W-4V-1La 2 O 3 and W-4Ti-1La 2 O 3 (wt.%) alloys have been produced by mechanical alloying and subse-quent hot isostatic pressing. Electron microscopy observations revealed that these alloys exhibit a submi-cron grain structure with a dispersion of La oxide nanoparticles. Large V or Ti pools with martensitic characteristics are found segregated in the interstices between the W particles of the respective alloys. Microhardness tests were carried out over the temperature range 300-1073 K in vacuum. The microhard-ness-temperature curve for W-4V-1La 2 O 3 exhibited the expected decreasing trend with increasing tem-perature although the microhardness stayed constant between 473 and 773 K. The W-4Ti-1La 2 O 3 presented quite different temperature dependence with an anomalous microhardness increase for tem-peratures above 473 K.