  In this paper, we obtain a blow up criterion for strong solutions to the 3-D
compressible Naveri-Stokes equations just in terms of the gradient of the
velocity, similar to the Beal-Kato-Majda criterion for the ideal incompressible
flow. The key ingredients in our analysis are the a priori super-norm estimate
of the momentum by a Moser-iteration and an estimate of the space-time square
mean of the gradient of the density.
  In addition, initial vacuum is allowed in our case.
