The mechanical performance of weldments is controlled by the properties of the fusion zone, heat-affected zone, and base metal.  However, the constitutive properties of these regions are not always easy to determine.  For large welds, conventional or subsize tensile samples can be extracted directly from the weld for testing.  This provides the most direct method for measuring the constitutive properties of individual weld zones, but is usually not possible in laser welds, and especially dissimilar metal laser welds.  Digital image correlation (DIC) methods have been developed and used to determine the constitutive tensile stress-strain response in laser welds in PH13-8 Mo to 304L and in 13-8 to 13-8 with various starting heat treatments (without weld heat treatment).  Both continuous-wave (CW) and pulsed (PW) laser welds were examined.  Testing was conducted in the transverse (cross-weld) orientation and samples were ground smooth to eliminate geometric effects (weld root notch) and to facilitate comparison with the base metal.  The DIC method provides quantitative 2-dimensional strain maps of the deformation field across transverse weld samples throughout tensile testing.  Local stress-strain response was extracted from various regions and compared to base metal response.  As expected, steep strain gradients were observed in the test welds, but constitutive relationships could be extracted for the various weld zones and compared with earlier work on 304L to 304L welds.  Metallographic analysis and electron backscattered analysis was used to quantify the microstructure and its relationship to the constitutive properties.  Digital image correlation has been shown to be a powerful technique for assessing the mechanical behavior of dissimilar metal laser welds, and the technique provides sufficient resolution to differentiate the constitutive properties of the various weld zones, and the relationships to microstructural features.  The technique is also suitable for examining the mechanical response near weld defects, such as isolated pores.