The friction of Nylon 6-6 against steel is studied in order to deal on correlations between tribological and chemical aspects. Thanks to surface analysis, we determine three different compositions on the surface of an injection-moulded sample, depending on the preparation techniques of the polymer, namely: -a polymeric surface, -an hydrolysed surface with adipic acid, hexamethyldiarnine and water, -the presence of cyclic oligomers which diffuse to the surface from the bulk. At low sliding speeds and normal loads, the friction coefficient oscillates between 0.1 and 0.7, and friction is governed by the extreme surface composition given by XPS (X ray photoelectron spectroscopy). At high speeds and severe conditions, the degradation of the polymer is due to surtemperature using in the contact. The high friction coefficients found are reliable to viscoelastic effects of Nylon 6-6, and to adhesion of acid groups to the metal surface. So we were able to correlate some chemical aspects to friction of Nylon 6-6 polymer against steel.