  We investigate the effect of the cosmological QCD transition on the evolution
of primordial density perturbations. If the phase transition is first order,
the sound speed vanishes during the transition and density perturbations fall
freely. The Harrison-Zel'dovich spectrum of density fluctuations develops large
peaks on scales below the Hubble radius at the transition. These peaks above
the primordial spectrum grow with wavenumber and produce cold dark matter
clumps of masses less than $10^{-10} M_\odot$. At the horizon scale the
amplification of overdensities is of order unity, and thus no $1 M_\odot$ black
hole production is possible for a COBE normalized scale-invariant spectrum.
