The stress-induced martensitic deformation and variant conversion (due to straining in the martensite state) of a Ti-50.8% Ni shape memory alloy will be studied. Macroscopic strain measurements indicate that the structure of stress induced martensite in this alloy is twin free. In-situ, low temperature tensile and compressive deformation is proposed for examination for both stress induced and simple cooling induced martensitic samples. Thus, by examining the neutron diffraction spectra before, during and after these deformations we will reveal whether stress-induced martensite has a twinned or twin-free structure.