The orientation of maleic anhydride-grafted poly(methyl-n-propylsilane) (PMPrS-g-MAH) in monolayers at the air/water interface is investigated by polarized UV absorption spectroscopy. The absorbance ratio of the semirodlike conformation of PMPrS to a random one shows inverted-V-shaped dependence on grafting yield. Dichroic ratio, which indicates the orientation of the monolayers, exhibits the similar dependence on grafting yield. This fact indicates that the orientation is closely related to the conformation of polymers constituting monolayers. The orientation of PMPrS-g-MAH monolayers is influenced also by the subphase temperature. As the temperature increases to T(m) of PMPrS, the dichroic ratio increases. However, the direction of the orientation abruptly changes around T(m), and then the monolayers come to show no orientation above T(m). This result demonstrates that the subphase temperature is a significant factor to obtain highly oriented monolayers. The orientation of PMPrS-g-MAH in LB films is also revealed, and highly oriented LB films are successfully obtained.