Method of producing knitted outerwear slacks of thermoplastic fibers, of permanently finished natural fibers, or of a thermoplastic and natural fiber blend, comprising knitting on a medium diameter circular knitting machine to seamless tubular knitted fabrics one after another, the circumference of the fabric being equal to one trouser leg circumference, the trouser legs having at least at one of their ends a double welt, separately heat molding said tubular knitted fabrics on individual molds to the final shape of the trouser legs, and then connecting both trouser legs together by one seat seam in the slacks seat and crotch portion, cutting away the remaining material between said seam and the waistline of said slacks to form the crotch portion, and finishing the slacks by making-up operations.