  I describe here the performances of a parallel treecode with individual
particle timesteps. The code is based on the Barnes-Hut algorithm and runs
cosmological N-body simulations on parallel machines with a distributed memory
architecture using the MPI message passing library. For a configuration with a
constant number of particles per processor the scalability of the code has been
tested up to P=32 processors. The average CPU time per processor necessary for
solving the gravitational interactions is within $\sim 10 %$ of that expected
from the ideal scaling relation. The load balancing efficiency is high
($\simgt90%$) if the processor domains are determined every large timestep
according to a weighting scheme which takes into account the total particle
computational load within the timestep.
