The defect structure forming during deformation of the fcc polycrystalline solid solution Cu-Al and Cu-Mn with different grain sizes (10-240 µm) was studied by TEM. Plastic deformation of the alloy samples was carried out in tension at rate of 2 × 10 −2 sec −1 at the temperatures of 293-573 K. The scalar dislocation density and its components (the density of geometrically necessary dislocations and the density of statistically stored dislocations), the size of dislocation cells and the curvature-torsion crystalline lattice were measured. Both the average parameters of all the samples and the local ones were determined at various distances from the grain boundaries.The study showed the presence of a hardened zone near the grain boundaries, the size of which decreases with a decreasing grain size.K e y w o r d s :