The Class A thermophilic anaerobic digestion improvements at the Orange Water and Sewer Authority¡¦s (OWASA¡¦s) Mason Farm wastewater treatment plant (MFWWTP) were brought on line in October and November of 2000. The process was stabilized and producing Class A quality biosolids in April of 2001. When the process stabilized, it was the first operational Class A anaerobic digestion plant in the United States of America. There have a been a number of papers published recently on projects that are either in development, under construction, or that have recently come online describing new process configurations to produce Class-A biosolids using thermophilic anaerobic digestion. Some of the more recent process upgrades include: „X Inland Empire Regional Plant Number 1 (online since 2002) „X Los Angeles Hyperion (online since January 2003) „X Los Angeles Terminal Island (online since early 2004) „X Madison, Wisconsin Nine Springs (scheduled for startup in 2005) „X Columbus (Georgia) CBFT3 (scheduled for startup in 2006). This paper summarizes operating data collected from the first 3 years of the MFWWTP¡¦s digestion operation.