The thermophilic digestion system at the Mason Farm WWTP in Chapel Hill North Carolina was brought on line in August 2000. This unique facility has the ability to produce class-A biosolids. The 12-mgd Mason Farm WWTP is operated by the Orange Water and Sewer Authority (OWASA) and treats an average of 8.5 mgd. The Mason Farm WWTP process and operation to achieve Class A status has changed considerably since the most recent publication on the process in 1996 (Willis, et al., 1996). This paper updates the basis of operation and Class-A qualification while providing operation data on the process.