The high voltage transmission and distribution lines are a source of electromagnetic fields, which may produce adverse effects on humans. Consequently, the magnitudes of the electric and magnetic fields are of increasing interest in a variety of situations, thus making it worthwhile to develop generalpurpose software that estimates both the electric and magnetic fields generated by power lines accurately. This paper deals with the simulations of the electric and magnetic fields under 500 kV lines. The simulations are carried out by Matlab for a horizontal conductor arrangement under balanced and unbalanced conditions, and for a vertical conductor arrangement. The results are compared with the IEEE standard for safety levels with respect to human exposure to electromagnetic fields.