INTRODUCTION The qualification, or requalification, ofan aseptic manufacturing facility depends in large part on the demonstration of controlled microbial conditions. The following are several areas where this is especially true: • Cleaning studies • Contamination control planning (1) • Equipment hold time studies (establishment of clean and dirty hold times~process hold times are process-speCific) • Selection of sample sites for environmental monitoring • Establishment of facility-relevant alert and action levels for controlled environments.