A brief history is followed by a description of a typical mains-voltage fluorescent lamp and the principles of its operation. Its high electric power-to-light conversion efficiency and the outstanding colour quality of the light are examined, together with conventions whereby these are assessed.As an example the 200/250-volt 80-watt lamp and its auxiliaries, marketed in this country in March 1940 to improve factory lighting in blackout conditions, are described in detail, and the characteristics of the components and the complete unit explained.It is concluded that this lamp is satisfactorily fulfilling a present industrial need, and that its quality has been so greatly appreciated that it is undoubtedly the forerunner of a new series of lighting lamps.