Method of manufacturing a film blowing-extrusion sheet in a film blowing-extrusion plant, having the following steps: a. extruding a tubular film; b. inflating the tubular film in a tube forming zone and taking off the double-layer film sheet with a take-off roller pair (2, 57) for drawing the tubular film in the longitudinal and transverse directions, c. cooling the rising tubular film with a cooling means, d. laying flat the tubular film to form a double-layer film sheet by means of a lay-flat device, e. guiding the double-layer film sheet further upward above the take-off roller pair (2, 57) and through a treatment-roller path (8, 50, 63) with a heating means for heating the double-layer film sheet, f. treating the double-layer film sheet in the treatment-roller path (8, 50, 63), namely drawing the double-layer film sheet in a drawing portion of the treatment-roller path (8, 50, 63), g. guiding the double-layer film sheet through a reversing unit for positioning; characterized by the additional step of h. controlling the film thickness of the double-layer film sheet drawn monoaxially in the machine direction within the drawing portion by means of a predefined desired thickness profile, the film thickness profile of the tubular film produced in the film blowing-extrusion plant being controlled such that the predefined desired thickness profile shows deviations from a uniform film thickness which are used for compensating for the film-thickness alteration over the film width which is produced during subsequent monoaxial drawing in the machine direction, so that by stretching, a film with a transverse thickness profile having as little deviations as possible from the average film thickness over the entire film width is produced. a. extruding a tubular film; b. inflating the tubular film in a tube forming zone and taking off the double-layer film sheet with a take-off roller pair (2, 57) for drawing the tubular film in the longitudinal and transverse directions, c. cooling the rising tubular film with a cooling means, d. laying flat the tubular film to form a double-layer film sheet by means of a lay-flat device, e. guiding the double-layer film sheet further upward above the take-off roller pair (2, 57) and through a treatment-roller path (8, 50, 63) with a heating means for heating the double-layer film sheet, f. treating the double-layer film sheet in the treatment-roller path (8, 50, 63), namely drawing the double-layer film sheet in a drawing portion of the treatment-roller path (8, 50, 63), g. guiding the double-layer film sheet through a reversing unit for positioning; characterized by the additional step of h. controlling the film thickness of the double-layer film sheet drawn monoaxially in the machine direction within the drawing portion by means of a predefined desired thickness profile, the film thickness profile of the tubular film produced in the film blowing-extrusion plant being controlled such that the predefined desired thickness profile shows deviations from a uniform film thickness which are used for compensating for the film-thickness alteration over the film width which is produced during subsequent monoaxial drawing in the machine direction, so that by stretching, a film with a transverse thickness profile having as little deviations as possible from the average film thickness over the entire film width is produced.