Leibovitz's L-15 Medium was specifically designed to grow cells in a CO2-free atmosphere. The standard sodium bicarbonate/CO2 buffering system is replaced by a combination of free basic amino acids, phosphate buffers, and higher levels of galactose and sodium pyruvate. As a result, the medium does not require supplementation with sodium bicarbonate and can be used under conditions of free gaseous exchange with the atmosphere. The medium can be used to grow human tumor cells and embryonic cells and also established cell lines such as HeLa and Hep-2.

The culture medium has been supplemented L-Alanyl-L-Glutamine in place of  L-Glutamine.

Compared with Glutamine, L-Alanyl-L-Glutamine is much more stable than L-Glutamine, releases less ammonia in culture, and improves cell viability and growth.

Leibovitz's L-15 Medium is frequently used in diagnostic virology where tissue cell lines or strains need to be grown in closed systems. Leibovitz's medium obviates the need of frequent medium change.

Users are advised to review the literature for recommendations regarding medium supplementation and physiological growth requirements specific to different cell lines.