Lidar techniques represent the most suitable tool to obtain information on the aerosol vertical distribution and therefore to close this kind of observational gap. Lidar networks are fundamental to study aerosol on large spatial scale and to investigate transport and modification phenomena. These are the motivations why EARLINET, the European Aerosol Research Lidar Network, was established in 2000, as a research program funded by the European Commission in the frame of the 5th framework program. After the end of the project, the network activity continued on the base of a voluntary association. At present, EARLINET consists of 25 lidar stations distributed over Europe. On March 2006, the EC Project EARLINET-ASOS (Advanced Sustainable Observation System) started on the base of the EARLINET infrastructure. This infrastructure project will enhance the operation of the network. EARLINET data can contribute significantly to the quantification of aerosol concentrations, radiative properties, long-range transport and budget, and prediction of future trends on European and global scale. It can also contribute to improve model treatment on a wide range of scales and to a better exploitation of present and future satellite data