Radio Frequency Identification (RFID) provides the basis for the envisioned "internet of things" and ubiquitous computing. Numerous publications, exposing new potential threats or providing safeguards to them, appear every year, creating a diverse research field. We study this available literature in the RFID field and give an overview of the trends in RFID research and provide a number of observations on RFID. The first part of this thesis gives an introduction to RFID and describes the basic functions of RFID. The following part examines available literature reviews on either RFID or security. Subsequently, we will study the current state of the art in RFID research and observe a number of facts that influence RFID research. Finally, this thesis gives a small statistical overview and a simple classification of the examined literature.