A molded thermoplastic resin disc substrate specially adapted for use with floating head type recording/reproduction apparatus is provided. The molded disc substrate has surface smoothness characteristics which are the same or better than are provided with mirror polished aluminum discs. The molded disc substrates include a floating head scanning surface wherein the maximum projection height or maximum surface irregularity is less than about 50 nm to reduce or eliminate damage to either the disc or floating head caused by unwanted collisions between them. In a preferred embodiment, the molded disc substrates are molded from a thermoplastic resin composition containing 10000 particles/gram or less of particles having a particle diameter of 0.5 .mu.m or more. In a preferred embodiment, control of particle size and content is achieved by subjecting the resin molding composition to a sequence of filtering steps using filters of decreasing mesh size.