Abstract: A process for eliminating in plastic materials odor/taste-producing substances is described, the plastic material especially having the shape of water pipes, plastic containers or plastic film/sheeting for packing foodstuffs and pharmaceutical preparations, or interior fittings of plastic. In the process, there is added, during processing in the molten state, less than 0.5 wt.-%, preferably 0.05-0.3 wt.-%, of a substantially hydrophobic aluminum silicate molecular sieve having a pore diameter of at least 5.5 .ANG., an Si/Al molar ratio in the crystal lattice of at least 35, preferably 200-500, and a sorption capacity for water at 25.degree. C. and 4.6 torr of less than 10 wt.-%, to the plastic material which subsequently is formed. The molecular sieve preferably has an average particle size not exceeding about 5 .mu.m. The plastic material is a polyolefin plastic and is preferably selected among ethylene plastics and propylene plastics.