This paper deals with an assessment of current distribution along vertical antenna penetrating the ground. The model is based on the integro-differential equation of Pocklinghton type together with rigorous Sommerfeld representation of the fields due to an interface. The corresponding integral equation is treated with the Galerkin-Bubnov variant of Indirect Boundary Element Method. The antenna is excited by the voltage source, as well as by the equivalent current source, which is incorporated into the model as a boundary condition.