Published online by Cambridge University Press: 01 December 1997
A construction is described of a 153-dimensional representation of the triple cover of O'Nan's sporadic simple group, over the field of order 4. This is then extended to a 306-dimensional representation of 3·O'N[ratio ]2 over GF(2). A similar construction in characteristic 3 gives an unrelated representation of the O'Nan group in 154 dimensions over GF(3), which extends to O'N[ratio ]2 provided that the field is extended to GF(9).