Abstract: An improved method and apparatus for the preparation of a thermoplastic foam having an enlarged cross-sectional area of a given geometric configuration. A heat-plastified foamable gel of a thermoplastic resin containing a blowing agent is extruded through an orifice of a die into a shaping channel. As the gel expands into a foam generally filling the channel and advances in the longitudinal direction, the foam is supported on a cushion of gas in the area of the channel, relatively near the die orifice, where the surface of the foam is sticky. A sufficient restraining force is applied to the foam in the area, where the foam surface is generally non-sticky, to exert a force in the direction opposite to the normal longitudinal advancement of the foam thereby forcing the foam to expand to a cross-sectional area greater than that of a foam allowed to expand freely. The expanded foam is then cooled to a generally self-supporting condition.