The CRISPR/Cas9 gene editing system was originally derived from the prokaryotic adaptive immune system mediated by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated proteins (Cas). The system has been successfully applied to genome editing in eukaryotes and has contributed to remarkable advances in the life sciences, in areas ranging from agriculture to genetic disease therapies. For efficient editing and extending the influence of this system, proper delivery of its components is crucial. Both viral and nonviral delivery methods are reviewed here, along with the advantages and disadvantages of each. In addition, we review ex vivo and in vivo CRISPR/Cas9 applications for disease therapies. Related remarkable studies are highlighted and relevant startup companies and their drug development pipelines are described. (C) 2017 American Institute of Chemical Engineers