This communication outlines the potential of variable-temp. Fourier transform near IR (FT-NIR) spectroscopy to study in situ the anisotropy induced in polymers by mech. deformation. For this purpose, a series of poly(dimethylsiloxane) (PDMS)/polycarbonate (PC) copolymers with varying compns. and block lengths were investigated by simultaneous mech. and Fourier transform near IR (FT-NIR) spectroscopic, so-called rheo-optical, measurements during cyclic elongation-recovery procedures between +22 DegC and -55 DegC. Depending on the compn. and block lengths of the block copolymers, different orientation and recovery phenomena were obsd. for the hard (PC) and soft (PDMS) segments and, for the first time, strain-induced crystn. of the PDMS-segments was derived from online FT-NIR spectroscopic measurements at -55 DegC.