For clinical hepatocyte transplantation, cells need to be prepared in a sterile GMP environment. Strict regulations are in place that set the standard for this environment that cells are prepared in. These regulations control all aspects of the environment. In the United Kingdom, the laboratory must have a licence from the Human Tissue Authority to prepare cell for clinical administration. The physical parameters such as air quality, pressure, temperature and microbiology counts have to be monitored regularly usually through direct measurement. Described here are the methods for microbial monitoring of the laboratory environment and the isolated cell preparations.