  We analyze the capability of prompt photon production in pp and pp(bar)
collisions to constrain the gluon distribution of the proton, considering data
from fixed-target experiments as well as collider measurements. Combined fits
are performed to these large-p_T direct gamma cross sections and lepton-proton
deep-inelastic scattering data in the framework of next-to-leading order
perturbative QCD. Special attention is paid to theoretical uncertainties
originating from the scale dependence of the results and from the fragmentation
contribution to the prompt photon cross section.
