This chapter examines the literature concerning media choice and partisan polarization. The past few decades have seen enormous growth in the number of television and internet news sources, giving consumers dramatically increased choices. Previous research has suggested two distinct links between media choice and partisan polarization: partisan media as a reflectionof polarization, as partisans self-select into media that conforms with their preexisting views, or as a causeof polarization, when outlets present one-sided stories that persuade people to adopt more extreme views. This chapter discusses how the literature in these two research traditions has diverged, as well as more recent research attempting to bridge this divide. Using novel methods, these studies have drawn together both self-selection and causal research designs to provide a more complete picture of media choice effects, and expanded the literature to more recent mediums, including the internet and social media.