Nonequilibrium three-dimensional (3-D) turbulent boundary layers are studied using direct numerical simulation (DNS). Time-developing flows are used to investigate the physics of spatial-developing ones. We find that application of a spanwise shear leads to the reduction of both the turbulent kinetic energy and drag, with the most dramatic reduction of the latter occurring when the shear is applied between y +≈ 5 and 15. When the three-dimensionality is produced by transverse skewing, the resulting alteration of the relationship between the Reynolds stresses is associated in large part with the effect of the pressure gradient upon the amplification or attenuation of the turbulent kinetic energy.