Most, if not all, of the studies that report cognitive impairments in patients who have been treated with cancer chemotherapy also report deficits involving the visual system (e.g., visual-spatial function or visual memory). The visual system seems like a likely susceptible target of cytotoxic drugs. Therefore, some portion of the vision-related cognitive deficits ofchemo fog/chemo brain might result from a direct action of the drugs or from site/site interaction between effects on the visual system and other critical brain regions. This chapter is a succint summary of a more expanded review.