Abstract: The surface of items which are penetratable for high-frequency energy, like for instance plastic food packagings which are manufactured by blow molding or vacuum molding, and in particular returnable bottles for soft drinks, are sterilized by providing a liquid film on the items, following which they are subjected to microwaves or high-frequency to heat the liquid film, preferably to the boiling point. The liquid is preferably water with a de-tensioning agent. An apparatus for performing the method is provided with wetting means, dripping off means adapted to leave a liquid film on the items during the dripping off, and heating means. The dripping off means are substantially constituted by transport means for conveying the items from the wetting means to the heating means. A system for sterilizing plastic bottles may compromise a washing section, a rinsing section, transport means adapted to let the bottles drip off during transport, and a heating section.