Abstract
Let G be a finite simple group and GK(G) be the prime graph of G. The
connected component of GK(G) whose vertex set contains 2 is denoted
by $\pi_1(G)$. In this paper, our purpose is to classify the finite simple
groups G such that $\pi_1(G)$ is regular. We prove that $\pi_1(G)$ is regular if
and only if all the connected components of GK(G) are cliques.