A box model for investigating the chemistry and growth of submicron particles in the marine boundary layer was developed. Processes simulated by the model were gas phase chemistry, in-cloud sulfate production, gas-to-particle transfer of condensable vapors, coagulation, dry deposition of particles and gases, and entrainment between the boundary layer and the free troposphere. According to model simulations, the most influential factor for the growth of nuclei and Aitken mode particles is the production rate of methane sulfonic acid (MSA) and other low-volatility compounds in the gas phase. Processes controlling SO2 concentrations dictate the amount of non-sea-salt sulfate produced in the boundary layer but are less important for particle growth. The ratio of MSA to non-sea-salt sulfate in the particulate phase may vary largely, even when a constant MSA yield from dimethylsulfide (DMS) oxidation is assumed. Clouds decrease nuclei lifetime but do not affect their growth significantly, unless the time between two cloud passages is very short. Sources other than DMS may produce condensable vapors that assist particle growth to some extent. With our current knowledge of the concentrations of condensible matter in the marine boundary layer, however, it seems unlikely that small nuclei are able to grow into cloud condensation nuclei size over their lifetime. More information is needed on heterogeneous surface reactions that may occur between submicron particles and vapors such as SO2, as well as on potential transport limitations between condensable vapors and particles caused by thermodynamics or organic surfactants.¿ 1997 American Geophysical Union