Abstract: A method and system for providing for the production of preforms of thermoplastic resin by filling a plurality of multiple-cavity molds with molten resin for forming the preforms, holding and cooling down the molten resin inside the molds, removing the molded preforms from the molds, subjecting the preforms to a subsequent temperature conditioning stage, and transferring the preforms to a blow-molding stage. Each of the multi-cavity molds includes a plurality of cavities defined in several distinct clusters and each cavities belonging to the same cluster is cooled in a distinct and differentiated manner with respect to the cavities belonging to other clusters provided in the same mold.