Simple groups, permutation groups, and probability J. Amer. Math. Soc. 12 (1999), 497-520. Martin W. Liebeck Department of Mathematics, Imperial College, London SW7 2BZ, England and Aner Shalev Institute of Mathematics, Hebrew University, Jerusalem 91904, Israel Abstract. We derive a new bound for the minimal degree of an almost simple primitive permutation group, and settle a conjecture of Cameron and Kantor concerning the base size of such a group. Additional results concern random generation of simple groups, and the so-called genus conjecture of Guralnick and Thompson. Our proofs are based on probabilistic arguments, together with a new result concerning the size of the intersection of a maximal subgroup of a classical group with a conjugacy class of elements.