Niobium-Titanium-Silicon alloys offer great potential as a new generation of refractory material system that could meet the high-temperature capability envisaged to exceed the application temperatures of Ni base superalloys. One of the serious concerns in the application of Nb based alloys is their poor oxidation resistance at elevated temperatures. Alloying of Nb with Ti, Si, etc. lead to multiphase microstructures containing silicides in BCC solid solution matrix and these alloys possess a good combination of mechanical properties at elevated temperatures and greatly improved oxidation resistance at these temperatures. Microstructural evaluations have revealed that selectively high internal oxidation of the BCC solid solution phase occurs in these systems. This study was initiated to examine the effect of this non-uniform distribution of internal oxidized regions on the tensile strength of Nb alloys. Two alloys, Nb-30Ti-7Si-10Cr-10Al-1Hf-1.5Zr-0.08C and Nb-30Ti-3Al-10Cr-1Hf-2Sn-0.5Si, the former a two phase alloy and the latter a single-phase solid solution alloy were examined. Micro-tensile samples were fabricated from various regions of oxidized samples and tested at room temperature and these results are compared with unoxidized samples. The influence of oxidation products on the tensile strength and the fracture morphologies of various samples will be discussed and demonstrated.