For sums of radicals Pk i=1 i di p i, where i; i are elements of some real algebraic number eld Q( ); di p i 2 R; we present a deterministic polynomial time algorithm to decide whether the sum is zero. The time is polynomial in the number of bits required to represent , the i's, i's and di's. The algorithm can be extended to sums of complex radicals over certain complex algebraic number elds. This research was supported by the ESPRIT Basic Research Action No. 3075 (ALCOM II). A preliminary