0. Ore (Math. Ann. 99. 1928, 84-I 17) developed a method for obtaining the absolute discriminant and the prime-ideal decomposition of the rational primes in a number field K. The method, based on Newton’s polygon techniques, worked only when certain polynomials /i(Y), attached to any side S of the polygon, had no multiple factors. These results are generalized in this paper finding a much weaker condition, effectively computable, under which it is still possible to give a complete answer to the above questions. The multiplicities of the irreducible factors of the polynomials /;( Y) play thtn an essential role.