An algebra is homogeneous if
the automorphism group acts transitively on the one dimensional subspaces of
the algebra. The purpose of this paper is to determine all homogeneous
algebras of dimension 4. It continues previous work of the authors in which all
homogeneous algebras of dimensions 2 and 3 were described. Our main result is the
proof that the field must be GF(2) and the algebras are of a type previously
described by Kostrikin. There are 5 non-isomorphic algebras of dimension 4; a
description of each is given and the automorphism group is calculated in each
case.