Ideally, formulation development of biopharmaceutical protein therapeutics will provide a final dosage form that offers sufficient ex vivo stability during processing, handling, and long-term storage and also provide adequate in vivo stability in terms of bioavailability that meets the pharmacokinetics/pharmacodynamics (PK/PD) therapeutic requirements. This chapter focuses on ex vivo stability of protein therapeutics and is targeted for the novice researcher who struggles with the inherent instabilities of biological molecules. More important, this chapter provides the inexperienced formulators with fundamental understanding and the basic tools for formulation development of biopharmaceutical proteins.