An apparatus for the simultaneous measurement of flow birefringence, extinction angle and shear stress in flowing, moderately concentrated polymer solutions is described.The instrument is essentially a concentric cylinder viscometer with ancillary optical equipment. It has several novel features: (i) the base of the rotating outer cylinder is stationary, (ii) the inner cylinder is supported on a special spring system allowing a small rotation under small torques but having high rigidity to other displacements, (iii) the separate components in the optical system may be rotated separately or together by accurately known amounts by a novel system.Some preliminary results on solutions of poly(methyl methacrylate) in dimethyl phthalate and polyisobutylene in decalin are presented.