We present measurements from events with two isolated prompt photons in 
pbar-p collisions at $\sqrt{s} = 1.8$ TeV.
The data were accumulated to an integrated luminosity of 4.3 1/pb.
Dominant backgrounds to prompt photons are single neutral mesons decaying into 
multiple photons, which are dissociated from jets.
To subtract the backgrounds, the photon identification by the lateral shower 
profile measured with the strip chamber embedded in the central electromagnetic 
calorimeter is applied to the data.
We obtain 49 +- 15(stat) +20-14(syst) events in the 
final diphoton data set.
The diphoton events include 1.8 +- 0.6 jets with transverse energy of 
4.5 +- 1.9 GeV on average, but no large missing transverse energy.
Thus the two-photon system have transverse momentum of 5.1 +- 1.1 GeV/c on 
average.
The event topology of diphoton production is comparable with that of W boson 
production.
The cross section for photons with transverse momentum pT in the range of 
10 < pT < 29 [GeV/c] is 
95 +- 28(stat)+38-27(syst) pb.
The differential cross section, measured as a function of pT of each photon, 
is about 3 times what a next-to-leading-logarithm calculation predicts.