Curable perfluoropolyether rubber compositions are provided comprising (A) a linear perfluoropolyether compound containing at least two alkenyl groups and having a perfluoropolyether structure containing recurring units --C.sub.aF.sub.2aO-- in its backbone, (B) an organosilicon compound containing at least two SiH groups, (C) an inorganic powder capable of chemical and/or physical adsorption of acidic gases and/or sulfur-containing gases, and (D) a hydrosilylation catalyst. The compositions cure into rubber or gel products having minimal permeability to acidic gases and sulfur-containing gases.