Photoinduced optical anisotropy due to molecular reorientation in hemicyanine Langmuir-Blodgett multilayers has been investigated by polarized UV-visible absorption and rotation-angle second harmonic generation measurements. Under polarized UV nanosecond laser illumination, the hemicyanine molecules reorient and align their chromophore axes along the direction of the UV beam polarization. Annealing of the films leads to randomization of the molecules and possibly dissociation of aggregate species.