Abstract: A method of forming multi-walled plastic containers in a single blow mold. In general, the method comprises disposing at least two separate parisons simultaneously into a blow mold and forming them to shape one after another by means of a special blow mandrel or pin. A substantially hollow, cylindrical first parison may be disposed around or outside of a substantially balloon or tube shaped second parison in an initially open blow mold. After closing the blow mold, the first or outer parison is expanded outwardly so that its outer surface engages the inner surface of the blow mold to assume the shape thereof, and thereafter, the second or inner parison is blown or outwardly expanded to an extent such that its outer surface at least partially engages the inner surface of the first or outer parison. The outer and inner parisons may be formed of different materials which may desirably impart different properties such as mechanical stability and resistance to permeation of fuel vapor from the container.