Abstract: Surveillance and target acquisition (STA) form one of the five key sub-systems that combine to make up a guided weapon (GW). This paper addresses the role of STA in GW systems. It identifies the key principles that can be used to select an STA sub-system to suit a particular application. A classification of types of STA is then proposed and finally, some of the GW-STA interface problems are discussed, including the issue of keeping the human somewhere in the STA-GW decision loop.