The Haute-Provence Observatory (44¿N, 6¿E) lidar facility has been extended to study the atmospheric lithium and its isotopic ratio Li7/Li6 in the upper atmosphere. The experimental features have been improved in order to lower the detection limit to 3.105 cm-2 for the total abundance with a resolution of 1.2 km in the altitude profile. The night-time measurements have been carried out from November 1977 to December 1979 and show some characteristic trends. The seasonal variation of the total abundance is similar to the one observed for sodium. The altitude profile is variable during the night. Total abundance fluctuations and peaks with small scale heights (1.5 km) are observed on numerous occasions. The layer is sensitive to high-altitude artificial releases, like CAMEO in November 1978, and to implying meteor showers. It is concluded that study of the behavior of atmospheric lithium and sodium should further our understanding of the alkali-metals chemistry.