A sterile, concentrated (100×) solution intended for use with EpiLife® medium to culture human corneal epithelial cells. HCGS is an ionically-balanced supplement containing bovine pituitary extract (BPE), bovine insulin, hydrocortisone, bovine transferrin, and mouse epidermal growth factor. Each 5 ml bottle of HCGS contains all of the growth factors, hormones, and tissue extracts necessary for the culture of human corneal epithelial cells, and is the correct amount of supplement for a 500 ml bottle of medium. When a 500 ml bottle of medium is supplemented with HCGS the final concentrations of the components in the supplemented medium are: • bovine pituitary extract (BPE), 0.2% v⁄v • bovine insulin, 5 µg⁄ml • hydrocortisone, 0.18 µg⁄ml • bovine transferrin, 5 µg⁄ml • mouse epidermal growth factor, 1 ng⁄ml