Recent developments of the multilevel physical optics (MLPO) algorithm aiming at the comprehensive analysis of complex reflector antenna systems are presented. The physical theory of diffraction (PTD) line integral along the rim of a reflector is combined with the physical optics (PO) surface integral within the multilevel algorithm. The multilevel scheme is also generalized to combine fields radiated by various components of different sizes, as encountered in complex antenna systems with multiple feeds and/or reflectors. Comparison with published results demonstrates the ability of the MLPO algorithm to cope accurately and efficiently with realistic reflector antenna problems.