This paper describes an application of Physical Optics and the Method of equivalent currents to the calculation of radar cross section (RCS) of a helicopter rotor. The problem is treated using a quasi-stationary approach. The calculation can be parameterized as a function of the locations of the radar transmitter and receiver in relation to the rotor center. Therefore, this offers the possibility of monostatic and bistatic simulations in the far field and near field. Blade geometry is taken into account using a triangular meshing generated by the I-DEAS meshing software. Digital applications are presented and the effects on the RCS spectrum of incidence, frequency, blade number, and the near field are analyzed. Index Terms--Method of equivalent currents (MEC), monostatism-bistatism, near field-far field, physical optics (PO.), radar cross section (RCS), RCS spectrum, rotating blade.