We have developed a Raman lidar system that is designed to make both daytime and nighttime measurements of atmospheric water vapor and aerosols. The three-channel lidar system’s laser operates at the third harmonic of Nd:YAG. The lidar uses narrow band-pass filters to measure (1) the elastic backscattered and pure rotational Raman signals, (2) the Raman scattered photons from nitrogen molecules, and (3) the Raman scattered photons from water vapor molecules. The lidar is a part of a comprehensive atmospheric properties measurement facility in Beltsville, MD. One of the primary purposes of the lidar is to characterize the temporal and vertical distribution of water vapor and dynamics processes in the boundary layer for evaluation of mesoscale models. The lidar is also used to measure cirrus cloud optical depths. These, as well as other, data obtained by the lidar system are a part of the overall measurement efforts at the Beltsville site operated by Howard University. Our lidar will also be used as a part of a regional network of lidar systems. We report here on the technical specifications and design considerations of the lidar system. We also discuss the results of the first operation of the lidar which was conducted as a part of an intensive measurement campaign held at the facility June 20-29, 2004.