A mathematical model of the benthic boundary layer is formulated and explored. Emphasis is placed on the near-bottom region, where recent field measurements have revealed the existence of a viscous sublayer. Field measurements have also indicated that form drag, due to roughness elements, may be an important feature of the boundary layer. The mathematical model includes submodels for low Reynolds number effects and form drag effects due to roughness elements and is thus intended to be applicable both to the viscous part of the flow and to the drag force dominated one. Verification studies are presented both for the viscous domain and the drag force dominated regions. Data from laboratory experiments are used for this purpose. Comparisons with field measurements of the benthic boundary layer are also presented as well as some principal balances of forces of the boundary layer, as predicted by the model. The general conclusion from the study is that the mathematical model presented describes the observed features of the benthic boundary layer in a satisfactory way. ¿ American Geophysical Union 1988