A measurement of the cross section for the inclusive production of isolated photons by the CDF experiment at the Fermilab Tevatron collider is presented. The measurement covers the pseudorapidity region |ηγ|<1.0 and the transverse energy range EγT>30  GeV and is based on 2.5  fb−1 of integrated luminosity. The sample is almost a factor of 7 larger than those used for recent published results and extends the EγT coverage by 100 GeV. The result agrees with next-to-leading order perturbative QCD calculations within uncertainties over the range 50<400  GeV, though the energy spectrum in the data shows a steeper slope at lower EγT.