We present results from a study of double diffraction
dissociation in p anti-p collisions at the Fermilab Tevatron performed by the
CDF Collaboration. The production cross section for events with a central
pseudorapidity gap (overlapping eta = 0) of width Delta eta0 > 3 is found
to be 4.57 +/- 0.02(stat)+0.99_ -1.19(syst) mb {5.45 +/-
0.02(stat)+1.10_ -1.17(syst)mb] at s**(1/2) = 630 [1800] GeV. Our results
are compared with previous measurements and with predictions based on Regge
theory and factorization.