The low-latitude boundary layer (LLBL) comprises a large fraction of the magnetospheric boundary layer making it a potentially important site for the transport of mass, momentum, and energy from the magnetosheath into the magnetosphere. We have used an ideal magnetohydrodynamic computer simulation with nonperiodic inflow and outflow boundary conditions to investigate the processes responsible for the spatial development of a 6.4 Earth radii (RE) long section of the dayside LLBL. Initializing the simulation with a realistic boundary layer configuration, slightly modified for computational efficiency, leads to the development of a LLBL which broadens with downstream distance from a thin (0.12 RE thick) and laminar boundary layer to a broad (~0.7 RE thick) and turbulent one capable of significant transport. Broadening occurs through the action of Reynolds and Maxwell stresses that develop during the roll-up and merging of vortices generated by the Kelvin-Helmholtz instability in the simulated boundary layer and indicates the transport of mass, momentum, and energy into the LLBL. The steep gradients that develop at the magnetopause between the vortices may further aid the transport by encouraging wave-article diffusion processes capable of transporting magnetosheath plasma into the LLBL. The presence of a flow-aligned component of the magnetic field, on the other hand, can hinder downstream development of the boundary layer by slowing and then stopping boundary layer vortices through transfer of their rotational kinetic energy into deformations of the magnetic field. ¿ American Geophysical Union 1993