The intercalation reaction of natural phospholipids into synthetic mica was examined by means of chemical analysis and X-ray diffraction analysis. The rate of the intercalation was fast from a chloroform solution of lipids, and bilayer formation in the solid phase was perfect. On the other hand, the rate of intercalation was rather slow in ethanol solution, and bilayer formation was not always successful. Such a solvent effect was accountable due to the solvation of the hydrophilic quaternary ammonium head either in the solution phase or in the solid phase.