The report describes measurements of atmospheric attenuation with an eye-safe lidar at 1.55 µm wavelength. The aim has been to show how a rangefinder can be modified to get an estimate of the atmospheric particle attenuation at the laser wavelength. Via model approaches, the particle attenuation at other wavelengths can also be estimated. In bad weather (visibility < 3 km), the attenuation is relatively constant for different optical wavelengths, while for clearer weather, empirical relationships for the wavelength dependance can be used. Different methods for estimating the atmospheric attenuation were investigated. Measurement against fixed unresolved targets in the terrain (e.g. house wall or ground) provide the opportunity to estimate attenuation as well as to analyze the backscattered signal from the atmosphere. With the single-target method, the attenuation against the same target in clear weather is compared to that obtained in worse weather. If you use two targets and take the ratio between the signals, you can estimate attenuation in a dynamic scene, for example from an airborne platform. The relative error in estimating the attenuation can be kept low even if the target reflectivity is not known. To verify the values of estimated attenuation from the backscattered lidar signal, the local visibility value at the laser's position was obtained from a weather station. The relationship between attenuation at the laser wavelength and the local visibility value was obtained from established atmospheric models. For horizontal trajectories, the attenuation estimated from lidar was compared with that derived from the local visibility value. Correlation was relatively good with a measured correlation coefficient of 0.76. Measured signal to noise ratio (SNR) against fixed targets (house walls) correlated well with the theoretical value of SNR based on the measured attenuation from lidar. The correlation coefficient for linear adaptation was here 0.77. A correlation coefficient close to 0.7 was obtained between the attenuation derived from visibility meter and those from measurements against a single target. A correlation coefficient of 0.63 was obtained between attenuation derived from the single-target and the two-target methods. Or from echoes from fixed targets. Furthermore, methods of inverting the lidar signal to obtain an attenuation profile along the entire beam path have been tried as well as illustrating data for oblique paths in a polar plot showing the distribution of attenuation at different elevations (1, 15, 30 and 45 degrees). In conclusion, measurements carried out show the potential of modifying laser rangefinders so that they can record and process backscatter from the atmosphere or from fixed targets to derive atmospheric attenuation. In this way, one can predict the ability of own or enemy optical sensors even for elevated paths and during dark conditions. Measurements on hard target may also serve as tools for estimating atmospheric extinction and these may be a complement to the backscatter methods.