CRISPR/Cas gene editing makes it much easier to make targeted changes in the DNA of human cells than other forms of gene therapy. This revolutionary technology offers spectacular opportunities to study gene functions; the clinical consequences of gene variations in patients can be determined much faster. The efficacy and accuracy of CRISPR/Cas is so impressive that a breakthrough to therapeutic applications is approaching fast. CRISPR/Cas is already being used in immunotherapy against cancer, and trials for monogenetic blood disorders, such as beta-thalassemia, have been scheduled. However, broad clinical implementation of CRISPR/Cas is not feasible yet, due to off-target DNA changes that may occur as a by-product. Particularly in case of in-vivo applications there are therapeutic challenges. For gene editing in human embryos, technical shortcomings and open ethical issues need to be addressed. Gene-editing therapy for serious disorders with transplantable cell types, and therefore the option of verification of "CRISPRed" cells, is seen as a possible first application within the regular healthcare system.