We reformulate a conjecture of Deligne on 1-motives by using the integral weight filtration of Gillet and Soul´ on cohomology, and prove it. This implies e the original conjecture up to isogeny. If the degree of cohomology is at most two, we can prove the conjecture for the Hodge realization without isogeny, and even for 1-motives with torsion. j Let X be a complex algebraic variety. We denote by H(1) (X, Z) the maximal mixed Hodge structure of type {(0, 0), (0, 1), (1, 0), (1, 1)} contained in j j H j (X, Z). Let H(1) (X, Z)fr.
