(Sodium fluorine mica)/nylon 6 composites were fabricated by the polymerization of 6-aminocaproic acid (ACA) and epsilon-caprolactam (CPL) mixed with the mica. The basal spacings (d(b)) of the mica in mica/(ACA + CPL) and mica/nylon 6 were 14-15 Angstrom and 21-22 Angstrom, respectively. The d(b) value of the latter composite indicates the intercalation of three nylon layers. On the other hand, by adding aluminum hydroxide sol (AHS) to the mica before mixing with the monomers, the d(b) value in the resulting mica/AHS/(ACA + CPL) increased up to similar to 30 Angstrom. After the polymerization of this mixture, the mica/alumina/nylon 6 showed a basal spacing of 31 Angstrom or no XRD peak of mica, depending on the composition. This basal spacing indicates that five nylon layers were intercalated in the mica. The viscosity average molecular weight of the nylon 6 in the composite decreased with increasing mica content.