A lidar-transmissometer intercomparison was made during an international experiment held in the German Alps to characterize the vertical structure of aerosols and clouds. The transmission path was 2325-m long and inclined at 30 deg along the slope of a steep mountain ridge. The transmissometer consisted of a Nd:YAG and a CO2 laser located in the valley and a large-mirror receiver that captured the full beams on the mountain top. Two lidars, one at 1.06 ?m and one at 1.054 ?m, were operated with their axes approximately parallel to the transmissometer axis but separated by a horizontal distance of the order of 20 to 40 m. The first lidar was operated in retroreflector mode and the relative transmittance was determined from the reflection off the mountain ridge above the cloud layer. The second lidar had a special receiver designed to make simultaneous recordings at four fields of view. The range-resolved scattering coefficient and effective cloud droplet radius are calculated from these four-field-of-view measurements by solving a simplified model (Bissonnette and Hutt, 1995) of the multiply scattered returns. The two simultaneous solutions for the scattering coefficient and effective droplet size make possible extrapolation at wavelengths other than the lidar wavelength of 1.054 ?m. The main measurement event analyzed lasted 1.5 h and produced transmittances ranging from less than 5% to more than 90%. The comparisons show good correlation between the transmissometer data and all lidar solutions including extrapolation at 10.59 ?m. The experiment also indicates the possibility of doing active imaging through optically thick clouds and demonstrates that lidars can measure turbulence structures in the atmosphere.