2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/11756We summarise the current status of cosmic microwave background spectrum and anisotropy measurements, and their theoretical interpretation. This is the update of the mini-review for the 1997 web-version of the Review of Particle Properties.5 pages of Plain TeX, including 7 figures (3 colour) using epsf. Also available at http://pdg.lbl.gov/Astrophysicstext