The advent of depth-resolving, remote measurement techniques for the determination of atmospheric constituents added a new dimension to the investigation of atmospheric phenomena. In the present paper optical, or lidar, techniques suited for this purpose are reviewed. After a presentation of the processes used and the algorithms necessary to extract the interesting information from the optical return signals, a few considerations about the necessary instrumentation are presented. For iilustration, one example is shown of results obtained with elastic backscatter, differential absorption and scattering, Raman lidar, and Raman DIAL. Of the numerous new developments in actual progress, one example, BELINDA, has been chosen that in a way marks the borderline between elastic backscatter and differential absorption lidar.