  The $\phi^4_3$ model at finite temperature is simulated on the lattice. For
fixed $N_t$ we compute the transition line for $N_s \to \infty$ by means of
Finite Size Scaling techniques. The crossings of a Renormalization Group
trajectory with the transition lines of increasing $N_t$ give a well defined
limit for the critical temperature in the continuum. By considering different
RG trajectories, we compute $T^c/g$ as a function of the renormalized
parameters.
