  We review the experimental results obtained by the NA49 collaboration in the
context of its beam energy scan programme. The data on particle yields and
spectral distributions suggest that the deconfinement phase transition is first
reached in central collisions of heavy nuclei at about 30A GeV beam energy.
Hadron-string transport models as well as the hadron gas model fail to describe
the observed energy dependences unless additional parameters or unmeasured
states are included.
