  We report Monte Carlo results for the two-dimensional hard disk system in the
transition region. Simulations were performed in the NVT ensemble with up to
1024^2 disks. The scaling behaviour of the positional and bond-orientational
order parameter as well as the positional correlation length prove the
existence of a hexatic phase as predicted by the
Kosterlitz-Thouless-Halperin-Nelson-Young theory. The analysis of the pressure
shows that this phase is outside a possible first-order transition.
