FT-IR spectroscopic measurements (polarized transmission and reflection absorption spectra (RAS)) of N-octadecylacrylamide (ODA) LB films indicate that ODA molecules are oriented nearly perpendicular to the surface of the plate; moreover they are ordered in the plane along the dipping direction (in-plane order). That is, ODA LB films have a high biaxial orientation. A drastic dichroism in polarized FT-IR caused by the large anisotropic arrangement of ODA molecules was observed, whereas that was not observed for the corresponding acrylate derivative.