Abstract. Let K be an algebraic number field of degree d 3, σ 1 , σ 2 , . . . , σ d the embeddings of K into C, α a non-zero element in K , a 0 ∈ Z, a 0 > 0 andLet υ be a unit in K . For a ∈ Z, we twist the binary formGiven m > 0, our main result is an effective upper bound for the size of solutions (x, y, a) ∈ Z 3 of the Diophantine inequalitiesfor which x y = 0 and Q(αυ a ) = K . Our estimate is explicit in terms of its dependence on m, the regulator of K and the heights of F 0 and of υ; it also involves an effectively computable constant depending only on d. §1. Introduction and the main results. Let d 3 be a given integer. We denote by κ 1 , κ 2 , . . . , κ 38 positive effectively computable constants which depend only on d. Let K be a number field of degree d. Denote by σ 1 , σ 2 , . . . , σ d the embeddings of K into C and by R the regulator of K . Let α ∈ K , α = 0, and let a 0 ∈ Z, a 0 > 0, be such that the coefficients of the polynomialare in Z. Let υ be a unit in K , not a root of unity. For a ∈ Z, define the polynomial f a (X ) in Z[X ] and the binary form