The work presented in this chapter has shown how to take advantage of the microDoppler features of the rotary parts of a helicopter. Traditionally, analysis of the amplitude variations of the target echo returns have been used in order to separate fixed wing and rotary wing aircraft. Modern radar systems are exploiting more signal processing, thus affording the extra costs of the Doppler processing. By applying the so-called short-time Fourier transform (STFT) to a data set, we can extract both amplitude variations (as a function of time) and Doppler contents from the signal, and thus more information will be available for target classification. The work has been focusing on the properties of helicopter micro-Doppler results from real-life systems, touching the dependency on monostatic and bistatic systems, frequency, geometry, and waveform. RCS modeling results from generic helicopter blades have shown the effects of frequency choice as well as geometrical dependence of the flashes from both main and tail rotor. Common models ranging from a box-like rotor to a high-fidelity CAD model of a generic helicopter blade demonstrated the required model accuracy as a function of frequency.