  In this paper, I present a precise Quantum Monte Carlo calculation at finite
temperature for a very large number (many thousands) of bosons in a harmonic
trap, which may be anisotropic. The calculation applies directly to the recent
experiments of Bose-Einstein condensation of atomic vapors in magnetic traps. I
show that the critical temperature of the system decreases with the
interaction. I also present profiles for the overall density and the one of
condensed particles, and obtain excellent agreement with solutions of the
Gross-Pitaevskii equation.
