abstract: Finding a uniform bound for the order of torsion points on an abelian variety over a number field is open and only the elliptic case is known (Merel). The situation is similar over function fields. Closely linked is the conjecture of Lang-Silverman that predicts a lower bound for the Neron-Tate height. This conjecture is open in all case over number fields and known only in the elliptic case over function fields (Hindry-Silverman). We shall describe these questions and describe a strategy towards these problems over functions fields.