A young turbulent spot develops in a spatially developing direct numerical simulation of an incompressible constant‐pressure boundary layer exposed to a strong localized disturbance. The data are analyzed to determine both the gross characteristics of the spot and the substructures that develop inside the spot. The calculations confirm that hairpinlike vortices are added near the trailing edge of the spot. However, the computations also suggest that the importance of large spanwise vorticity structures may have been overestimated by previous experiments. The current simulation data reveal that streamwise vortices are more intense and more numerous. In addition, the streamwise vortices provide at least one route for the entrainment of near‐wall fluid into the turbulent spot near the leading edge. ©1996 American Institute of Physics.