  The atmospheric muon spectrum between 20 and 2000 GeV was measured with the
L3 magnetic muon spectrometer for zenith angles ranging from 0 to 58 degrees.
Due to the large data set and the good detector resolution, a precision of 2.6%
at 100 GeV was achieved for the absolute normalization of the vertical muon
flux. The momentum dependence of the ratio of positive to negative muons was
obtained between 20 and 630 GeV.
