Human embryonic stem cells (ESCs) would provide a potentially unlimited source for cell replacement therapies. However, the molecular mechanisms involved in the maintenance of "stemness" are not fully understood. Monkey ESCs are much more similar in character to human ESCs than are mouse ESCs. Therefore, studies using monkey ESCs can give conclusions that are more relevant and may be readily applicable to both basic research and clinical applications for future regenerative medicine. For such studies, generation of a gene-inducible system regulatable in primate ESCs would serve as a powerful tool. Here, we established a Tet-Off gene-inducible system in monkey ESC lines. Such manipulated cells maintained ESC characteristics, and inducible gene expression in both the stem cells and differentiated cells could be reliably controlled by doxycycline administration.