Monolayers of alkyl side chain substituted poly(ferrocenylsilane) (FCSIOCT) have been studied for the first time. The monolayer behavior is found to be strongly temperature dependent and also to change distinctly when the monolayer is oxidized by addition of FeCl3 to the polymer before spreading. The zero pressure area per repeat unit for the unoxidized polymers is similar to 20 Angstrom(2) at 20 degrees C, which suggests that the ferrocene moiety must be excluded from the water surface and the silane repeat units with the aliphatic side chains alone occupy the surface area on the air-water interface. The FCSIOCT monolayer mixed with FeCl3 shows the liquid analogous state occurring at much larger areas, with a plateau region appearing in the isotherm at 44 mN/m. The zero pressure area in the liquid analogous state is similar to 45 Angstrom(2), which is almost equal to the theoretical area required for both the silane and ferrocene moieties to be at the surface. For both monolayers, the area per repeat unit continuously decreases with time at constant pressure. Monolayers transferred onto substrates have been studied using X-ray reflectometry. The thickness of the unoxidized FCSIOCT monolayer is higher than that of the oxidized monolayer. When the oxidized monolayer relaxes on the water surface, the thickness increases and approaches the thickness of the pure FCSIOCT monolayer.