This paper is intended to serve both as an introduction to radar cross-section measurements and as an introduction to the several measurement papers that follow in this issue. We discuss the contribution that experimental work makes to theoretical studies. The history of cross-section measurements is reviewed. Some terms are defined, and the major measurement problems are discussed. It is pointed out that the various range geometries and measurement techniques in use today were based on the approach used to solve the basic measurement problems. Some details are given of the more popular present-day measurement systems, i.e., CW, pulsed, FM-CW, Doppler, and the standing-wave ratio method.