2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198678We summarize the theory talks given in Working Group 4 `Polarized Lepton Nucleon Scattering' at the DIS 99 workshop. The significant progress made over the last year on many of the interesting topics in `spin physics' is documented.10 Pages, LaTeX, 6 figures as eps filesHigh Energy Physics - Phenomenologytext