We report the first results of the beam-spin asymmetry measured in the reac
tion (e) over right arrowp --> ep gamma at a beam energy of 4.25 GeV. A lar
ge asymmetry with a sin phi modulation is observed, as predicted for the in
terference term of deeply virtual compton scattering (DVCS) and the Bethe-H
eitler process. The amplitude of this modulation is alpha = 0.202 +/- 0.028
. In leading-order and leading-twist perturbative QCD, the alpha is directl
y proportional to the imaginary part of the DVCS amplitude.