Norway rats served for decades as the main subject species in studies of behavior, its development and its neuroanatomical and hormonal substrates. Tens of thousands of research papers were and are still being published in which Norway rats serve as subjects. Here, we first, discuss some of the reasons for the rise and fall of Norway rats as a focus of behavioral research, then describe the origins of the domestic rat and the natural history of its wild forebear before reviewing a few of the plethora of research areas in which Norway rats have participated.