This chapter on styrenic plastics covers a broad category of polymeric materials of which styrene is an important part. Chemical structures, manufacturers, and trade names along with typical end uses of the plastics are included besides extensive tabular and graphical permeation properties. Plastics included in this section are acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate (ASA), and styrene-acrylonitrile (SAN) copolymer.