Portions of the global cycles of sulfur and iodine could be intertwined in reactions resulting from the emissions of dimethyl sulfide (DMS) and methyl iodide. A two‐dimensional photochemical model of a marine tropical tropospheric synoptic system is used to analyze the consequences of these emissions through their atmospheric transformation cycles to aerosols. Following one line of analysis, the reaction of IO+DMS → DMSO+I could play a significant role, ∼30–50%, in destroying DMS, if the reaction proceeds at the published fast rate. Under these assumptions, the concentrations of DMSO (dimethyl sulfoxide), dimethyl sulfone (DMSO₂), and sulfate appear to set rather strict upper limits on the extent of the reaction over the global oceans, and hence, on [IO], which is < 2×10⁵ molecule cm⁻³. DMS plays an important role in the iodine cycle by converting IO into I. The formation of a reservoir species HOI, following H abstraction by IO, may help explain the high concentrations and apparent strong diurnal variation of filter‐sampled inorganic iodine gases and help to explain low [IO] values. In an alternate, preferred, line of analysis, the rate of reaction of IO+DMS may be much slower, < 10⁻¹² cm³ molecule⁻¹s⁻¹ and the I and S cycles remain decoupled: in this case, it appears that the OH+DMS addition reaction could proceed ∼30% to form DMSO. The mean concentration and variations of gaseous and particulate iodine species are also better simulated. A simple aerosol model describing fine and coarse particles is used to close the S budget, and, if only a minor role is played by DMSO, the budget compares well with data. Simulated SO₂ concentrations for the upper troposphere are highly dependent on upper tropospheric [OH]. The paper concentrates on remote tropical ocean regions and includes simulations of the spatial and diurnal variation of iodine species I, IO, HI, HOI, IONO₂, I₂O₂ and I_tot(particulate) the sulfur species DMS, DMSO, DMSO₂, MSA (methane sulfonic acid), SO₂, and SO₄⁼(particulate), as well as the species OH, HO₂, and H₂O₂.

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