Abstract: A fill pack for heat and mass transfer in counter-flow, in particular for the cooling of water in cooling towers by air, is provided. The fill pack includes a plurality of vertically or obliquely positioned corrugated or folded sheets or plates which are superposed and joined to each other in such a manner that the corrugations or folds of adjoining sheets cross each other only in the upper part of the fill pack, while the corrugations or folds of adjoining sheets are generally parallel to each other in the lower part of the fill pack.