A polymerization filling of a base in character monomer (epsilon-caprolactam) was carried out using fillers with solid acid character and catalytic action such as gamma-alumina and calcium phosphate. The properties and structure of the polymerization-filled polycaprolactam obtained were studied. The following characteristics were determined : melting temperature, glass transition temperature, crystallization temperature, tensile strength, and dynamic elastic modulus. The advantages of the polymerization filling method are shown as compared to conventional methods for homogeneous production of polycaprolactam.