The author outlines the history of the locus coeruleus from its discovery to the latest research findings. Although Russel's report in Texas has been believed to be the first break-through scientific article of this neuronal structure, there were two preceding, anatomical and physiological, studies made by Japanese groups. One of the aims of this review is to shed brief light on their works, which being written in Japanese so that might have been unfamiliar to most researchers in the world.