Lidar measurements, conducted at Hampton, Virginia, over the past 4 years, have provided data to characterize the mid- latitude stratospheric aerosol cloud produced by the Mount Pinatubo volcano in June 1991. These data also extend a long-term record on the stratospheric aerosol backscatter over the Hampton area dating back to 1974. Since shortly after the Pinatubo eruption, frequent measurements of aerosol backscatter have been taken using a 48-inch ground- based lidar facility at the NASA Langley Research Center in Hampton, Virginia. Aerosol backscatter ratios at 649 nm were measured throughout the 4-year period. In November 1992, a 532 channel was added to the 48-inch lidar, and backscatter ratio measurements were started for that wavelength as well as for 694 nm. Results show that integrated backscatter values increased to more than two orders of magnitude above background levels within about eight months after the Pinatubo eruption. These levels have gradually decreased since then, but some variations caused by seasonal influences have been observed. Recent measurements (December 1995) indicate that the aerosol loading has returned to approximately pre-Pinatubo levels. Over the time period that these measurements were conducted, a number of hardware modifications were made to enhance measurement capability of the Langley 48-inch lidar system, including the addition of a Nd:YAG laser, a more versatile detector package, and a Sun Sparcstation for automation and data analysis.