The electroadsorption and electrooxidation of CO on Fe have been studied at the following pH values : 14, 9.2, 6.9, and 3. In spite of the high oxidizability of Fe, a cathodic cleaning sufficed to produce an unoxidized surface on which CO could chemisorb. Over the whole pH range 3-14 chemisorbed CO was detected on the electrode surface as evidenced by an IR band at 1916-1993 cm(-1), which was assigned to linear (on-top) CO, Its intensity was about 0.2%, from which a surface coverage of 5-10% was estimated. This low CO coverage inhibited both hydrogen evolution and the electrooxidation of Fe itself, which was interpreted by assuming that the cathodic cleaning reduced the native Fe oxides only over a small fraction of the surface and that CO chemisorption, H-2 evolution, and start of Fe electrooxidation take place only on this small fraction of the surface.