Let C be a triangulated category.We first introduce the notion of balanced pairs in C,and then establish the bijective correspondence between balanced pairs and proper classes ξ with enough ξ-projectives and ξ-injectives.Assume that ξ:=ξx=ξy is the proper class induced by a balanced pair(X,y).We prove that(C,Eξ,sξ)is an extriangulated category.Moreover,it is proved that(C,Eξ,sξ)is a triangulated category if and only if X=y=0,and that(C,Eξ,sξ)is an exact category if and only if X=y=C.As an application,we produce a large variety of examples of extriangulated categories which are neither exact nor triangulated.