Serum is a complex mixture of large number of constituents differing in molecular weights, chemical nature and functions, and its supplementation is required in media formulations for culturing of hybridomas. Since fetal calf serum is fairly expensive, serum-free (completely defined) media or media formulations with reduced level of fetal calf serum arc being tested for growth of hybridomas and antibody production. Usefulness, limitation, and future scope of these media formulations are discussed.