Unitals in the code of the Hughes plane

A coding‐theoretic characterization of a unital in the Hughes plane is provided, based on and extending the work of Blokhuis, Brouwer, and Wilbrink in PG(2,q²). It is shown that a Frobenius‐invariant unital is contained in the p‐code of the Hughes plane if and only if that unital is projectively equivalent to the Rosati unital. © 2003 Wiley Periodicals, Inc.