Let p > 2 be a prime, denote by F-p the field with \F-p\ = p, and let F-p*
= F-p\{0}. We prove that if f is an element of F-p[x] and f takes only two
values on F-p*, then (excluding some exceptional cases) the degree of f is
at least 3/4(p - 1). (C) 2000 Academic Press.