  We describe a new implementation of a parallel Tree-SPH code with the aim to
simulate Galaxy Formation and Evolution. The code has been parallelized using
SHMEM, a Cray proprietary library to handle communications between the 256
processors of the Silicon Graphics T3E massively parallel supercomputer hosted
by the Cineca Super-computing Center (Bologna, Italy). The code combines the
Smoothed Particle Hydrodynamics (SPH) method to solve hydro-dynamical equations
with the popular Barnes and Hut (1986) tree-code to perform gravity calculation
with a $N \times logN$ scaling, and it is based on the scalar Tree-SPH code
developed by Carraro et al (1998)[MNRAS 297, 1021]. Parallelization is achieved
distributing particles along processors according to a work-load criterium.
Benchmarks, in terms of load-balance and scalability, of the code are analised
and critically discussed against the adiabatic collapse of an isothermal gas
sphere test using $2 \times 10^{4}$ particles on 8 processors. The code results
balanced at more than 95% level. Increasing the number of processors, the load
balance sligthly worsens. The deviation from perfect scalability at increasing
number of processors is negligible up to 64 processors. Additionally we have
incorporated radiative cooling, star formation, feed-back and an algorithm to
follow the chemical enrichment of the interstellar medium.
