ATLID (ATmospheric LIDar) is the ESA backscatter lidar instrument, prime candidate to be flown on a future European Earth observation mission. It will provide information on features of the Earth's atmosphere, such as top height of all cloud types and Planetary Boundary Layer aerosols, thin cloud extent, optical depth and depolarization. Based on the results of a pre- phase-A and two subsequent parallel phase-A studies, ESA decided in 1991 to initiate the ATLID Instrument Technology Predevelopment Program. It is broken into two stages: The first stage is devoted to concept selection, instrument design and breadboarding of critical technologies. The second stage will cover the design, development, assembly and testing of an advanced ATLID demonstration model. The first stage is further divided into a Phase 1, concept selection and preliminary design, which has been finished end of 1993, and a Phase 2, currently in progress, comprising the breadboarding of critical technologies and a final instrument design update. The selected instrument architecture is based on a one-axis scanning 60 cm telescope and a pulsed diode-pumped Nd:YAG laser transmitter. The estimated instrument volume, mass and power are 1.4 m X 1.6 m X 1.1 m, 200 kg and 450 W, respectively.