Abstract: Single-walled carbon nanotubes (SWCNTs) continue to fascinate the scientific community. However, any commercially available SWCNTs obtained directly from the viable synthesis procedures are mixtures of semiconducting and metallic species. That shortcoming of present technologies hinders further studies and limits the scalable applications for a series of promising SWCNT-based electronics. Separation of the two species is one way to solve the present dilemma. The methods and techniques used for the enrichment of semiconducting- and metallic-SWCNTs are reviewed. Their advantages and disadvantages are compared and commented on. We believe that the research emphasis on SWCNT separation will continue to pursue a technique with operational simplicity, high efficiency, low-cost that is easily scalable.