  Let G be a Mathieu simple group, s in G, O_s the conjugacy class of s and
\rho an irreducible representation of the centralizer of s. We prove that
either the Nichols algebra B(O_s,\rho) is infinite-dimensional or the braiding
of the Yetter-Drinfeld module M(O_s, \rho) is negative. We also show that if
G=M22 or M24, then the group algebra of G is the only (up to isomorphisms)
finite-dimensional complex pointed Hopf algebra with group-likes isomorphic to
G.
