An octadecanol monolayer on water was investigated with regard to surface pressure relaxation and area creep at 283 K. Under surface pressure less than 20 mN/m, the relaxation and creep completed within a few ten minutes and the monolayer showed a homogeneous morphology. The monolayer under higher surface pressure continued to relax. FT-IR spectra of monolayer films indicated that an absorption band of the CH₂ asymmetric stretching mode shifted to low energy with increasing the surface pressure. Molecules in the monolayers after pressure relaxation and area creep preferred to gauche-and trans-configuration, respectively. The compression and dilatation of the monolayer gave rise to a hysteresis curve in the surface pressure(II)-area(A) relationship and the dynamic viscosity measured by canal method was 2∼3×10^-6 Pa. s. m. These could be related with the gauche-traps transformation. The collapses of the monolayer were found at high surface pressure. Homogeneous octadecanol monolayers could be formed after creep at about 20 mN/m.