A step-frequency continuous waveform ground-penetrating radar (SFCW GPR) is a frequency-domain radar system based on a waveform consisting of a succession of sine waves at increasing frequency. In particular, the term “continuous wave” specifies that the transmission and reception of the signal at each frequency occurs simultaneously, unlike other step-frequency systems, such as gated GPRs. The main concept behind this particular technology is to obtain a large bandwidth pushed toward the lower end of the spectrum, overcoming the trade-off between penetration and resolution typical of impulse-based GPRs. The recorded raw data therefore represent the frequency response of the subsurface, and an inverse Fourier transform can be applied to obtain a synthetic trace in time domain. This chapter gives a brief overview of the SFCW technique applied to GPR, providing some insight into the characteristics of the hardware, the properties of the waveform, the relevant parameters for data collection, and the aspects related to the processing and postprocessing of the data. There are indeed not only similarities between SFCW GPR and impulse GPR but also substantial differences. Focusing on this diversity, the authors’ ambition is to reveal and eliminate some common misconceptions about the SFCW technique and provide an adequate background to get the most out of the data collected with this kind of GPR.