In this paper we are considering a general field defined in space-time by a second-rank antisymmetric tensor. We can have it depending on two potential vectors. From one variational principle, by varying the two potentials, all field equations are derived. When potentials are varied in a suitable way, we also obtain an expression of canonical energy-momeptum tensor. Several forms of Lagrangian density are considered; as particular cases, equations of known physical fields are found.