Unimolecular pathways for the isomerization and/or dissociation of HSOO, HOSO, HSO2, and HOGS to H + SO2 and OH + SO have been investigated computationally, as well as HSO formation via an HSOO intermediate. The atmospheric lifetime of HSO2 is discussed. Some pathways have no barrier, including OH + SO --> HOSO and H + SOO --> HSOO and SOOH, while structures and vibrational frequencies of transition states for HOSO --> H + SO2, HOGS --> OH + SO, HOSO --> HSO2, HSOO --> HS + O-2, and HSO2 --> H + SO2 have been characterized at the MP2 = FULL/6-31G(d) level. Some geometries were further refined at the QCISD/6-311G(d,p) level. Gaussian-2 theory was employed to calculate approximate QCISD(T)/6-311+G-(3df,2p) energy barriers, and the kinetics were analyzed by RRKM theory. Rate constant expressions at the high and low-pressure limits and thermochemical properties for transient intermediates are tabulated, and the results are discussed in the context of atmospheric and combustion chemistry. A revised theoretical H-OSO bond strength is compatible with the flame data for SO2-catalyzed recombination of H atoms.