Radiation in the terahertz range, loosely defined as 0.1 to 10 terahertz (THz), spans the relatively undeveloped gap between electronics at the low end of the spectrum, and optics at the high-frequency end. Initially, THz radiation was used exclusively by astrophysicists for applications such as the detection of antimatter. However, this extremely expansive and spectrally unique portion of the electromagnetic spectrum was of interest for such applications as space-based communications, upper atmospheric sensing and communications, and potentially for short-range terrestrial communications and nonintrusive package screening. More recently, radiation in the THz range has been identified as ideal for an extremely wide range of applications from security to medical systems. Moreover, the realization of THz transistors and the use of negative index materials, and more recently its use in counterfeit integrated circuit detection, may revolutionize THz technology. In this special section, we present a collection of selective papers that represents to a certain extent the recent advances in THz and related technologies.