The main results concern radicals and polynomial identities of rings w
hich are sums of two subrings. It is proved that a ring which is a sum
of a nil subring of bounded index and a ring satisfying a polynomial
identity also satisfies a polynomial identity. Filds which are sums of
two Jacobson radical subrings are classified. Several open questions
are answered. (C) 1998 Elsevier science B.V. All rights reserved.