For tetraphenylporphyrin derivatives substituted with four fluorocarbon chains (TFPP), monolayers on the water surface were studied with the Brewster angle microscope together with pressure-area curves; It was found that heterogeneous aggregated structures of the monolayers were dependent upon the chain length of fluorocarbons, the metal-free or Mn-TFPP, and the periods after spreading. Polarized W-visible spectra for the monolayer assemblies indicated that the porphyrin rings in the films were tilted on the average, but had a tendency to adopt an orientation more parallel to the water surface as the chain length of the fluorocarbon increased. The third-order nonlinear optical susceptibility for found to be 7.0 x 10(-13) esu, and those of Mn-TFPP were enlarged.