Although the history of atmospheric lidar starts in the early 60s, the history of optical radar for atmospheric studies is much older. The first suggestion that the scattering of light by atmospheric molecules could be used to measure the vertical profile of atmospheric density appears to have been made by Synge (1930), and the first attempt to implement the technique was made by Hulbert (1939) who was able to measure the light scattered from a searchlight beam at heights up to 28 km. In the 50s and early 60s Eltermann, working at what was then the Air Force Cambridge Research Laboratories (now Phillips Labs), made extensive measurements at heights up to 65 km using a modulated searchlight. The main limitation to this technique is that with a CW light source the only way of defining the range from which echoes are to be received is by separating the transmitter and receiver by about 30 km and adjusting the crossover height of their fields of view. Several workers (Johnson and Jones in the UK and Friedland in the US) tried to use pulsed flashlamps as a light source, but with limited success, and both concluded that the available light sources were unsuitable for the purpose. All this changed with the invention of the pulsed ruby laser by Maiman, in 1960, which led to the rapid development of lidar systems for probing the atmosphere. This presentation will concentrate on the early days of lidar when notable progress was made in a number of areas including Rayleigh scattering measurements for high altitude atmospheric temperature profiling, Mie scattering for tropospheric and stratospheric aerosols, Differential Absorption Lidar, mainly applied to ozone measurements, and resonant scattering for measuring meteor ablation products at mesopause heights.