Heterolytic and homolytic S_NO bond dissociation energies are determined in acetonitrile at 25 ℃ by using titration calorimetry and electrochemical measurements with a well designed thermodynamic cycle. The results suggest that S_NO compounds in vivo may release NO in a manner of homolytic bond dissociation. Other effects that influence the bond energies are also discussed. [WT5HZ] Heterolytic and homolytic S_NO bond dissociation energies are determined in acetonitrile at 25 ° C by using titration calorimetry and electrochemical measurements with a well designed thermodynamic cycle. The results suggest that S_NO compounds in vivo may release NO in a manner of homolytic bond dissociation. Other effects that influence the bond energies are also discussed. [WT5HZ]