Abstract: To ensure the consistency of quality in recombinant protein production, the cell bank for biologics should be derived from a single clone. A number of techniques have been used for cloning and assurance from the cellular pool after transfection with a target gene. Here, using CHO cell as an example, we summarize the knowledge and understanding of monoclonality of production cell bank from both industries and regulatory authorities, and propose general considerations on the requirements of monoclonality for clinical trial application and new drug application based on current techniques. Furthermore, we suggest quality control strategies and assessment methods for those cell banks from non-single clones.