Method for the sterilisation of a preform (10) made of plastic material, said preform (10) comprising both a neck (13) equipped with an opening (11) and a bottom (12) opposite to the opening (11). The method comprises the steps of:-introducing into the preform (10) an agent (15) intended to perform a sterilising action；-heating the agent (15) contained in the preform (10) in order to determine evaporation.The step of heating the agent (15) is preceded by a gripping step of the preform (10) by gripping means (2) acting on the outside of the preform (10). The gripping means (2) identify, in combination with the preform (10) itself, an annular cavity (3). The annular cavity (3) externally surrounds the neck (13) of the preform (10) and is in fluid communication with the inside of the preform (10) to allow the evaporated sterilising agent (15) to reach the outside of the neck (13).
