2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198642Recent theoretical results in tau lepton physics and their implications for the experimental analysis are presented. The paper is split into the following chapters: 1. Introduction, 2. Weak Couplings, 3. Inclusive Decays, Perturbative QCD and Sum Rules, 4. Exclusive Decays, 5. Beyond the Standard Model.Latex, 22 pages. Theoretical review, presented at TAU98, Santander, Spain, September 1998. The complete paper, including figures, is also available via anonymous ftp at ftp://www-ttp.physik.uni-karlsruhe.de/ttp98/ttp98-40/ or via www at http://www-ttp.physik.uni-karlsruhe.de/Preprints/High Energy Physics - Phenomenologytext