Measurements of lithium in stars of different galactic populations such as young open clusters (Alpa Per, Pleiades, Praesepe, Coma, Hyades), very young stellar associations (Taurus-Auriga, Chamaeleon, Ophiuchus clouds), intermediate and old open clusters (NGC 752, M 67, NGC 188), old disk stars, and halo stars give the observational framework from which the galactic evolution of lithium has to be inferred. This element is produced mainly via three mechanisms, including primordial nucleosynthesis, spallation reactions in the interstellar medium, and thermonuclear reactions in some particular stellar evolutionary stages (novae, red giants). The complicated nucleosynthesis and the fact that 'astration' of lithium in stars is not well understood, makes a direct interpretation of the lithium evolutionary abundance curve difficult. The constraints set by recent lithium measurements in very old open clusters and metal-deficient stars on galactic lithium production mechanisms are discussed. Current problems in the determination of the primordial lithium abundance are briefly reviewed.