The invention concerns a process for the production of hollow bodies of thermoplastic material by extrusion blow molding. In the process according to the invention continuous extrusion of at least two preforms in web form of plasticized material is effected by means of a plurality of extrusion devices. The preforms are jointly shaped to form a hollow body in the still plastic condition, that is to say in the first heat, within a multi-part tool forming a mold cavity. In that case a wall thickness profile is imparted to at least one preform during the extrusion operation independently of the respective other preform by continuous nozzle gap adjustment during the extrusion operation.