Abstract: Method for manufacturing plastic bottles, including the step in which respective preforms are removed from the respective moulds, and the step in which said preforms are transferred into temperature conditioning stations for a predetermined period of time, during which said preforms are caused to undergo an asymmetrical heat treatment that is effective in heating in a different manner a preform sector having an angular spread of a definite value that is anyway not less than 180°. The method includes the step in which said surface sector of the preform is heated up with the help of heating means that are partially arranged in a crown-like manner around the respective preform.