We present results from a measurement of double diffraction
dissociation in p anti-p collisions at the Fermilab Tevatron collider. The
production cross section for events with a central pseudorapidity gap of
width Delta eta0 > 3 (overlapping eta = 0) is found to be 4.43 +/-
0.02(stat) +/- 1.18 (syst) mb [3.42 +/- 0.01(stat) +/- 1.09(syst) mb] at
s**(1/2) = 1800 [630] GeV. Our results are compared with previous
measurements and with predictions based on Regge theory and factorization.