A prospective study concerning the tonometric viability supervision of 9 digestive free autografts after total pharyngolaryngectomy was conducted. This technic is based on the Henderson and Hasselbalch's equation which calculates the intramucosal pH (pHi) in the graft using a tonometric catheter. When the pHi is under 7.10, there is a graft ischemia. This invasive technique seems to be sensitive and specific provided that minimally rigorous measurement procedures are used. Late graft necrosis is the major limitation of the technique.