We have investigated several aspects of trace gas photochemistry in the marine boundary layer using a time-dependent transport-kinetics model with one-dimensional eddy diffusion. The photochemical scheme in the model (Thompson and Cicerone, 1982) is represented by a conventional complement of reactions involving O, H, N, and methane-derived organic species; boundary conditions are assigned which give low surface mixing ratios of O3 and NOx (Routhier et al., 1980; McFarland et al., 1979) characteristic of the remote marine environment. Altitude dependent eddy diffusion coefficients in the surface layer (1 mm to 100 mm) are based on the formulation of Businger et al. (1971) for temperature diffusively in an unstably stratified surface layer. Diffusion coefficients in the rest of the convective boundary layer (the mixed layer) are taken from Lamb and Durran (1978). The surface is assumed to be the tropical ocean with a steady state mixed layer. In the simulations described here, particular attention has been given to the distribution of odd nitrogen and the NO2-NO-O3 photostationary state in the surface boundary layer. Calculated profiles of NO, NO2, O3, and HNO3 show definite gradients in the surface layer. When the ocean is assumed to be a source of NO, mixing ratios on the order of a few parts per trillion can be supported by an upflux of ~108 cm-2 s-1. If a surface input of NO is not assumed, NOx levels are much lower. This is consistent with measurements in the Equatorial Pacific (McFarland et al., 1979); Zafiriou et al., 1980; Liu et al., 1983) and suggests that NO upwelling may be significant in the local budget of Nox in certain marine environments. Calculated values of the O3-NO-NO2 photostationary state ratio, Rps and NO/HNO3 show appreciable variation within the surface layer. The latter ratio is sensitive to the NO upflux and to hetergeneous removal of NHO3, Rps decreases away from the surface and is unity only at one point. Both chemical and micrometeorological factors (Lenschow, 1982) contribute to nonunity values of Rps. Significant departures from a profile characteristic of a nonreactive species are shown to occur in the NO profile as low as 0.2 m above the surface.