Abstract. Let B be the Lie algebra with basisIt is proved that an irreducible highest weight B-module is quasifinite if and only if it is a proper quotient of a Verma module. For an additive subgroup Γ of F, there corresponds to a Lie algebra B(Γ) of Block type. Given a total order ≻ on Γ and a weight Λ, a Verma B(Γ)-module M (Λ, ≻) is defined. The irreducibility of M (Λ, ≻) is completely determined.