A van-mounted ruby lidar system has been developed for the remote single-ended measurement of smoke plume transmittance at ranges of 150-500 m. The measurement of transmittance is obtained by comparing the clear air lidar return from the near side of the plume with that from the far side. The lidar system performance has been tested using synthetic targets of known transmittance, and its accuracy limitation has been found to be photomultiplier tube afterpulsing. Results from these target tests as well as field tests using real power plant smoke plumes where comparison telephotometer measurements were made are discussed in terms of accuracy for the determination of plume transmittance.