Arithmetical equivalence of fields and group actions ZHANG Ji-ping Abstract: As is known, prime decomposition in extensions of rational field is determined by some analytic object, namely Dedekind's zeta function. Two number fields are said to be arithmetically equivalent if they have the same Dedekind's zeta function. From the group theoretical point of view arithmetical equivalence of fields can be characterized in terms of the permutation characters of corresponding Galois groups. In this talk we will report some progress on this problem.