Cellular starting material is unique because of the living, dynamic nature of cells that must be collected from a human donor. The process for donor screening and testing to reduce risk of infectious disease transmission is complex and not harmonized globally. Biologic, donor-to-donor variability is difficult to control and has major impacts on development of the manufacturing process and final product specifications. Maintaining stability of the material requires attention to the complex supply chain for a given manufacturing model. This article presents the key elements, regulatory expectations and special challenges for qualification of cellular starting material.