Abstract. For a polynomial in several variables depending on some parameters, we discuss some results to the effect that for almost all values of the parameters the polynomial is irreducible. In particular we recast in this perspective some results of Grothendieck and of Gao.This paper is devoted to irreducibility questions for families of polynomials in several indeterminates x 1 , . . . , x ℓ parametrized by further indeterminates t 1 , . . . , t s . We assume that ℓ 2 and the base field k is algebraically closed; the more arithmetic case ℓ = 1 depends on the base field and involves different tools and techniques.Set(where k(t) is the algebraic closure of k(t)); F is said to be generically irreducible. The core question is about the irreducibility of the polynomials obtained by substituting elements t * 1 , . . . , t * s ∈ k for the corresponding parameters t 1 , . . . , t s -the specializations of F .More specifically we wish to investigate the following problem, as explicitly as possible: -when the generic irreducibility property is satisfied, show some boundedness results on the following set, which we call the spectrum of F :}, and some density results for its complement, -find some criteria for the generic irreduciblity property to be satisfied and deduce some new specific examples.A first approach rests on classical results of Noether and Bertini and a second one involves more combinatorial tools like the Newton polygon and the