A congruence for Jacobi sums of order k over finite fields is proved,
which generalizes a congruence of Iwasawa (1975) for prime k and Ihara
(1986) for prime power k. Related congruences for Jacobi sums are als
o presented. The techniques are elementary and self-contained, in cont
rast with the deep methods of Iwasawa and Ihara. (C) 1998 Academic Pre
ss.