The aim of the current paper was to systematically review the quality and design of the literature examining cognition and fitness to stand trial (FST). Ten empirical studies published between 1970 and July 2013 met the inclusion criteria. All studies utilised cross-sectional designs and six were prospective. Study quality was appraised based on FST research guidelines. The study quality was highly variable. Intelligence was controlled statistically in only half of the included studies. Cognitive processes, specifically, processing speed, verbal memory and visuoperceptual skills differentiated fit and unfit groups. Aspects of executive functioning, including social knowledge and abstract thinking, influenced FST. Future studies should use prospective consecutive designs and multivariate statistical strategies that control for potential confounds. Comprehensive assessment across a number of cognitive domains is needed in order to validate research conducted to date and guide forensic assessment of FST.