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The present study was induced by unexpected findings with this and other not fully substituted cellulose derivatives. Although fully transparent aqueous solutions were prepared, static light scattering ( L S ) revealed a strong aggregation.A detailed analysis of the LS-data as well as transmission electron-microscope pictures gave evidence for fringed micelles as aggregate structure. These particles consist of several side-by-side aligned chains that form a compact core from which many dangling chains emerge. The core in this model has a geometrical anisotropic shape and flow birefringence became detectable when orienting the particles by the action of shear forces. Induced flow birefringence is a common feature of many other materials and therefore a set-up was constructed that could be attached to a common constant stress rheometer of Bohlin. The reported experiments present first examples measured with this set-up and demonstrate the efficiency of this technique. In the following the equipment is briefly described and the results obtained so far are tentatively interpreted.