In this work the influence of alkylimidazoles on the electrochemical behaviour of carbon steel in stirred and aerated NaCl solution is studied. For all the organic compounds tested, the corrosion inhibition efficiency increases with concentration. The inhibition effect has been noticed to increase with the number of carbon atoms in the hydrophobic chain. The maximum corrosion inhibition efficiency was obtained with 11 carbon atoms. The low corrosion inhibition efficiency with long hydrophobic chains can probably be interpreted by deformation of the hydrophobic head destabilises the adsorbed layer. Results obtained with N-undecylimidazole showed that it acts cathodically at low concentrations and anodically at high concentrations. The maximum corrosion inhibition efficiency was observed about the critical micellar concentration (c.m.c). The establishment of a bimolecular layer film leads to a modification of the cathodic and anodic processes.