  The values of $R = \sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$
for 85 center-of-mass energies between 2 and 5 GeV were measured with the
upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider, with
an average uncertainty of $\sim7%$.
