Cosmic Ray Muon Physics
  We present a review of atmospheric and underground muon flux measurements. The relevance of these data for the atmospheric neutrino flux computation is emphasized. Possible sources of systematic errors in the measurements are discussed, focusing on the sea level muon data. Underground muon data are also reported. 
S. Cecchini (Istituto TESRE/CNR and INFN, Bologna) and M. Sioli   (University and INFN, Bologna)