NT 201 is a botulinum toxin type A preparation free of complexing proteins, i.e. free of proteins other than the active toxin. Injected into the muscle, NT 201 causes local weakening to full paralysis depending on the administered dose. Botulinum toxin type A is widely used for aesthetic treatment of facial lines. This study will determine the optimal dose of NT 201 in the treatment of glabellar frown lines.