Abstract: We study the large scale limit of 2D Monte-Carlo simulations of grain growth with isotropic grain boundary energy and mobility in the low temperature regime and show that the Monte-Carlo model converges to the deterministic Boundary Tracking model defined by the Mullins equation of curvature driven growth and the Herring balance condition. The convergence is illustrated by computer simulations at both the level of individual grains and the level of distribution functions. The von Neumann's $(n-6)$ rule is verified for individual Monte-Carlo grains in an average sense and a Fokker-Planck equation is shown to be useful in analyzing the distribution functions in both the Monte-Carlo and the Boundary Tracking simulations.