This chapter discusses two pulse compression techniques. It considers the correlation processing, which is predominantly used for narrowband and some medium-band radar operations and describes the stretch processing. Stretch processing, also known as active correlation, is normally used to process extremely high-bandwidth Linear Frequency Modulation (LFM) waveforms. Range resolution for given radar can be significantly improved by using very short pulses. Unfortunately, utilizing very short pulses decreases the average transmitted power, which can hinder the radar's normal modes of operation particularly for multi-function and surveillance radars. In pulse compression, it is desirable to use modulation schemes that can accomplish a maximum pulse compression ratio, and can significantly reduce the side lobe levels of the compressed waveform. Weighting functions can be used on the compressed pulse spectrum in order to reduce the sidelobe levels. The cost associated with such an approach is a loss in the main lobe resolution, and a reduction in the peak value.